T-License 2.x FAQ

License for T-Kernel 2.0 with greater flexibility
T-License 2.x(T-License 2.x、T-License 2.1、T-License 2.2)

As T-Kernel 2.0 has been released to the public, TRON Forum has issued "T-License 2.x" by revising T-License which is the terms and conditions for T-Kernel. The revisions are explained and applicable cases are examined. The distribution of μT-Kernel under the dual license of T-License 2.x and μT-License has begun since December 2011. Therefore, all the OSs distributed by TRON Forum can be used under T-License 2.x. The compatibility needs to be checked using test suite for μT-License. However, the check is not required for T-License 2.x. μT-Kernel suited to compact or small-scale embedded devices is expected to be used more widely under T-License 2.x.

Now, anyone can redistribute the source file.

T-Kernel is the OS used for embedded devices and naturally requires the license which is suitable for the development of embedded devices. "T-License" has been created for this reason.
For embedded systems development, some companies may improve the source code of the OS to use some special devices or to enhance the performance. As they have done such modification with their own know-how, they prefer not to disclose their source code.
GPL (GNU General Public License) is famous as an open source software license, but the source code of the derivative work must be provided if requested. On the other hand, as T-License does not require users to disclose such source code, it was very popular in the embedded systems community.
Based on the policy of "Single One Source" (meaning a single source from one master repository), TRON Forum was the only distributor, and developers could obtain the source code and modify it if necessary, and completed embedded device development. Developers also could create the system-dependent part to support a different CPU and distribute the part as a patch. As an exception, the organization which performed the procedure of "Register as a distributor of modified version" could release modified version.
However, developers were not allowed to distribute the source code alone in principle, which had been modified from the original source code.

●The License evolved together with T-Kernel 2.0
It has been nine years since the release of the first version of T-Kernel. Many embedded-type CPUs have adopted SoC design and the performance has been improved in the intervening years. In response to the hardware improvement, the specification of "T-Kernel 2.0," the evolved TRON OS has been designed. Finally, May 2011 saw the long-waited distribution of T-Kernel 2.0 to the public. At the same time, its license has been newly defined as T-License 2.x.

●The big feature is great flexibility
There are three major revisions in T-License 2.x.

1. Redistribution of the original reference source code is possible.
2. Distribution of modified source code is possible.
3. Conditions for the distribution of the modified source code can be specified by its developer.

As seen from the above, T-License 2.x offers greater flexibility than the original T-License. Item 2 above means users can distribute the source code modified still further based on the source code which has been distributed as modified one as well as distribute the modified reference source code.

●Traceability with ucode
With this flexibility, it may be hard to keep track of how the original source code has been modified through many modifications. Therefore, the service to trace the modification history is offered, and it is required to attach "distribution ucode" to the modified source code for distribution. Distribution ucode can be obtained and searched using the "T-Kernel Traceability Service" in the TRON Forum official webpage. When registering a new modified package, the user needs to record the distribution ucode of the distribution package which is the original of the modified package. There can be more than one parent. In addition, the link of information such as where to obtain or buy the source code can be registered.

●Supports business and private use
There are many types of users of T-Kernel 2.0. Some companies plan to bring their products developed based on T-Kernel 2.0 to the market. Some individuals offer to share their modified codes with some improvement.
To draw a clear line between such types of users, T-License 2.x handles distribution to a large number of specific persons through the Internet communication, broadcasting, and the like and distribution to the general public through the Internet communication, broadcasting, and the like automatically in response to a request from the public separately. The former is commercial distribution, and the latter is free distribution. For commercial distribution, the copyright of the modified part can be claimed. However, for free distribution, the rights of integrity of the moral right of an author can not be exercised.
This last point merits an explanation. Under the copyright laws in many countries including Japan (a notable exception is USA), modification of a literacy work is subject to the approval by the original author. However, T-License 2.x removes this restriction explicitly by permitting the recipients to modify T-Kernel 2.0 and redistribute it freely in the same manner as GPL does in the case of “free distribution.”

●Contribution to embedded systems industry is expected
Thus, T-License 2.x has the flexibility and is capable of meeting the different needs of many types of users. With the dissemination of T-Kernel 2.0, T-License 2.x is expected to contribute to the development of the embedded systems industry in the future.

T-License 2.x Q&A

Q1

I want to introduce T-Kernel to my acquaintances. Can I copy T-Kernel 2.0 downloaded from the T-Engine official webpage and give it to them without modification?

A1

Yes, you can. T-License 2.x allows users to redistribute T-Kernel 2.0 downloaded from the T-Engine official webpage without modification. It is important to redistribute the package without modification. You can copy the downloaded T-Kernel 2.0 to a CD to distribute it if necessary unless you modify the package by adding anything to it or taking anything out of it for redistribution. It is also important to ask the recipient to accept terms and conditions of T-License 2.x. For redistribution, there is no need to pay a license fee to TRON Forum or the owner of the copyright.

Q2

We hold embedded systems seminars. Is it OK to redistribute the downloaded T-Kernel 2.0 from the TRON Forum webpage to the participants as RTOS materials? Also, do we need to pay license fee in this case?

A2

Similarly to A1, you can redistribute the downloaded T-Kernel 2.0 without modification. There is no license fee for redistributing it either in free in-house trainings or fee-based seminars. Please make sure to ask the recipient to accept terms and conditions of T-License 2.x.

Q3

We hold embedded systems seminars. Is it OK to redistribute the downloaded T-Kernel 2.0 from the TRON Forum webpage to the participants as RTOS materials after removing some unnecessary features from the package?

A3

Yes, you can redistribute the downloaded T-Kernel 2.0. However, in this case, it is different from distribution without modification as some change is made to the original by "removing some unnecessary features." In T-License 2.x, "making some change" is equivalent to "modification." T-License 2.x allows users to redistribute the modified source code. For redistribution, register the original source version and obtain a unique code called "distribution ucode" using T-Kernel Traceability Service. Then, redistribute the source code after writing the distribution ucode in it. This allows those who obtain the modified source code to know what the original version of the source code is. When you obtain distribution ucode, you do not need to publish its source code. With T-Kernel Traceability Service, you need to register not the source code itself, but the location from which you can obtain the version of T-Kernel to which the distribution ucode is assigned, namely the inquiry contact information.

Q4

I'm planning to redistribute the source code modified from T-Kernel 2.0. If there are multiple versions of original source codes from which the modified one is derived, how do I register them?

A4

With T-Kernel Traceability Service, you can register multiple parent source code versions of the source code to be redistributed. Accordingly, when obtaining the distribution ucode of the modified source code, specify the distribution ucode of the multiple source codes. This allows users to know the extent of the impact of the modification to the parent versions which indirectly affects child and grandchild.

Q5

I have mixed the part of the source code of μT-Kernel with the source code of T-Kernel 2.0. In this case, how do I comply with the license?

A5

In case where the source code of μT-Kernel or of T-Kernel 1.xx is mixed with the source code of T-Kernel 2.0, it may be questioned about which license shall be selected between the existing T-Kernel License and T-License 2.x. To come right to the point, developers can choose the license to be distributed with their package for themselves. For redistribution according to T-License 2.x, please distribute the package by obtaining distribution ucode and writing the ucode in the package in the same manner as in A4. It is the same for downloading AMP T-Kernel and μT-Kernel distributed under T-License 2.x.

Q6

T-Kernel 1.xx and μT-Kernel are distributed under the dual license of T-License and T-License2.0. Under which license do I need to download them?

A6

Irrespective of the license under which you download T-Kernel, there is no difference in the source code itself. If you cannot decide which license to use in order to download, it is recommended to download under T-License 2.x as it allows you to redistribute T-Kernels more easily.

Q7

I've developed embedded devices using the source code of T-Kernel 2.0. Do I need to report it to anybody?

A7

No, you do not have to. If it is fine with you, we encourage you to announce your development using T-Kernel 2.0. If you consult with the TRON Forum secretariat, your development will be posted on the TRON Forum official website and introduced in this magazine. Note that if you use T-Kernel 2.0 for your development, you need to display the T-Kernel logo on the start screen of your embedded devices and indicate the use in your user manual in accordance with the "Obligation of indication of use." However, if you are the member of the forum, you can be exempt from this obligation if the application for exemption is submitted.

Q8

We are planning to sell the source code of T-Kernel 2.0 to our customer who develops embedded devices after tuning the code. Is there any problem with the license?

A8

No. There is no problem with the license. Also, those who tune the source code and the customer who obtain the tuned code do not have to be TRON Forum members. We encourage users to promote the use of T-Kernel 2.0 vigorously. Note that with T-Kernel 2.0 License, all users need to comply with the Obligation of indication of use. Therefore, please ask your customers to indicate the use of T-Kernel 2.0 in their embedded devices and user manuals as well as indicating it in your tuned source code of T-Kernel 2.0. It is the same for using T-Kernel 1.xx, μT-Kernel, etc. under T-License 2.x. If you have any questions, please contact the TRON Forum Secretariat.

Q9

Can the developer sell the modified source code via trading companies and distributors?

A9

Under T-License 2.x, the developer can re-distribute the modified source code including its “Derivative Work” if the developer modified itself the source code downloaded from the TRON forum site.

Related clause

• Article 3. 2 The Developer may perform the following acts with respect to the Source Code:
  • (6) to re-Distribute, whether with or without payment, the Derivative Work of the Source Code modified by the Developer itself pursuant to the paragraph (1) above to any third party, provided that the Developer shall comply with both of the following conditions:
• Article 3. 3 The Developer may perform the following acts with respect to the Derivative Work of the Source Code:
  • (4) to re-Distribute, whether with or without payment, the Derivative Work of the Source Code Distributed hereunder (excluding the Derivative Work of the Source Code Distributed in a manner as set forth in paragraphs (1) and (3) of Article 2.9) to any third party, provided that the Developer shall comply with both of the following conditions:
    The part in red in this clause is mentioned here to prohibit the developer from re-distributing the source code purchased for business use without prior consent, etc.

If the developer who modified the source code sells it to their customers via trading companies and distributors, License Agreement in relation to the use of source code shall be concluded between the developer who modified the source code and their customers. The trading companies and distributors are not required to conclude the License Agreement as the developer with their customers. In such cases, Article 3.2.6 applies.

Q10

Can the developer sell the source code modified by their outsourcee?

A10

Under T-License 2.x, if the developer modified the source code downloaded from the forum site itself, it (the developer) can re-distribute the modified source code including its “Derivative Work.” What if the developer outsource the work of modification ?

Related clause

• Article 3. 2 The Developer may perform the following acts with respect to the Source Code:
  • (6) to re-Distribute, whether with or without payment, the Derivative Work of the Source Code modified by the Developer itself pursuant to the paragraph (1) above to any third party, provided that the Developer shall comply with both of the following conditions:

In case the developer outsources the modification of the source code, it is practically regarded by TRON Forum that the outsourcee modifies the code in lieu of the developer. Both of them are required to register them on the source code download web page of TRON Forum and download the same T-Kernel so that the developer can sell the modified source code under Article 3.2.6.

Q11

Can the licensee sell their customer the modified source code provided by the licenser?

A11

Can the licensee sell their customer the modified source code provided by the licenser?
Yes, it (the licensee) can. License sales, which is popular in the embedded systems industry, is possible under T-License 2.x.

Related clause

• Article 3. 2 The Developer may perform the following acts with respect to the Source Code:
  • (6) to re-Distribute, whether with or without payment, the Derivative Work of the Source Code modified by the Developer itself pursuant to the paragraph (1) above to any third party, provided that the Developer shall comply with both of the following conditions:

The licensee can sell the modified source code. To make it possible, TRON Forum views the modification by the licenser as the modification by the licensee. To make this interpretation possible, the licensee needs to register itself at the source code download web page of TRON Forum and download the same T-Kernel as the licenser modified so that the licensee can sell the modified source code under Article 3.2.6. If the licensee further modifies the originally modified source code and document provided by the licenser, it (the licensee) needs to register itself at the traceability service and obtain a new distribution ucode.