KERNEL: Replace ST for license issue.

[winlinvip]

Please read https://github.com/ossrs/srs/wiki/LicenseMixing, we want to replace ST with some library or create a new one, because ST uses MPL 1.1 or GPLv2 LICENSE.

[winlinvip]

SRS won't replace ST, because the MPL LICENSE is ok.

[winlinvip]

Seems MPL is fine to used in MIT project, so we haven't to replace it.
The modified version of MPL retains the copyright of the original author, but there are no usage restrictions. It can be used in other licenses such as MIT or in commercial software. Reference:

1. Comparison of free and open-source licenses
2. Detailed Explanation of Open Source Software Licensing Agreements (GPL/MPL/LGPL/BSD/Apache Licence/Creative Commons/MIT)
3. License Agreements BSD GPL MPL LGPL APL

TRANS_BY_GPT3

[winlinvip]

Firefox is licensed under MPL, while Chrome uses the more permissive BSD license.

This video explains it very clearly.

1. MPL is a file-level license, unlike GPL which is a project-level license. Therefore, ST's files need to comply with the MPL license, while newly added files do not need to comply with the MPL license.
2. MPL-licensed files can be directly included in SRS (or statically linked), unlike LGPL which requires dynamic linking. This is because MPL is a file-level license, so other files in SRS can be considered as newly added files and will not be infected with MPL.
3. If you modify a file that was originally licensed under MPL, you must release it under MPL as well. This requirement is similar to GPL. So, if you modify SRS, it's not a problem, but if you modify ST's code, you must open-source it. Otherwise, you would be violating the MPL license (but SRS does not violate it because all modifications in SRS comply with MPL).

SRS supports linking ST as both static and dynamic libraries by default, with static linking being the default option. You can enable dynamic linking by using ./configure --use-shared-st=on. Both static and dynamic library linking are compliant with the regulations.

https://youtu.be/YlKtCDJquSw
https://www.mozilla.org/en-US/MPL/
https://blog.csdn.net/xiaoxiao133/article/details/83049959
https://zhuanlan.zhihu.com/p/118582418

Please note that the description of MPL in the following figure is not accurate. It does not clearly express that including files directly or linking MPL with static libraries is also compliant. It only states that newly added files do not have to be MPL.

TRANS_BY_GPT3

[winlinvip]

The MPL license is ok for SRS MIT, to use --shared-st=on.

sh-3.2$ ./configure -h|grep shared-st
  --shared-st=on|off        Use shared libraries for ST which is MPL license. Default: off