T-Kernel source code is available from the T-Engine Forum website. T-Kernel is available to anyone free of charge after the license agreement called "T-License" is accepted. It is free even if it is embedded into a product and hundreds of thousands of that product are sold. It can be modified to meet the needs of hardware in the product. Compared to other open source software licenses such as GPL (General Public License), T-License pays necessary attention to usage as an OS for embedded devices. GPL applies to derivative works of GPL'ed programs and the source of the derivative work must be provided if requested. On the other hand, T-License does not require users to disclose the source of a derivative work based on the original T-Kernel source. Users have the choices of not disclosing the part in which know-how is available, disclosing it only to specific customers, or disclosing it for profit. In other words, it is totally up to the user whether or not the source is disclosed. An overview of T-License is as follows.

1. The T-Kernel source code can be copied and modified freely without charge.
2. A modified or copied version can be included in a product in binary format and can be freely sold and distributed as a product. Even in this case, there is no need to pay a license fee.
3. It is necessary to display that T-Kernel is used in the product.
4. Users of the source code must agree to a T-License first before downloading it from the T-Engine Forum website.
5. When any source code is developed by improving or modifying the T-Kernel source code, registration is required to "distribute" the changed code to third parties.
6. Although it is guaranteed that the T-Kernel source code does not infringe on the copyrights of a third party, it is not guaranteed that it meets the purpose of the user and that it does not infringe on patents.
7. The T-Kernel source code is copyrighted. If any provision of T-License is violated, measures based on copyright infringement are implemented.

This T-License was revised on March 24, 2009 to meet the needs of embedded systems development further. The following points are the specific changes.

1. The stipulation that the existence of T-Engine and μT-Engine hardware is essential has been revised.
2. Smooth distribution of results when T-Kernel is ported to run on various hardware (CPUs) and to work with many compilers.
3. Distribution of header file is explicitly allowed to improve the developers' convenience.
4. "What cannot be done" as well as "what can be done" has been clarified for easier understanding.

CPUs are always continually evolving. We have received many requests for porting T-Kernel to new CPUs as well. In response to these requests, the progress of hardware development can be followed rapidly in the current revision with the additions of the "T-Engine-like hardware" definition and permitting the distribution of source code for hardware-dependent parts. The revision of T-License is not tied to a particular version of T-Kernel source code. If you would like to use T-Kernel under the revised license, please agree to the T-License once again and apply for download for use. At present (as of December 9, 2009), the source code distributed from the T-Engine Forum under T-License or licenses compliant with T-License are T-Kernel, T-Kernel Standard Extension, AMP T-Kernel, SMP T-Kernel, T-Kernel, AMP T-Kernel Standard Extension, and SMP T-Kernel Standard Extension. These source codes can be downloaded by applying for them at T-Engine forum website (http://www.t-engine.org/).