mbedTLS

官网:
https://tls.mbed.org/
许可证:
Apache 2.0 license  https://tls.mbed.org/how-to-get

CyaSSL

官网:
http://freshmeat.sourceforge.net/projects/cyassl
许可证:
GPLv2 Commercial

wolfSSL

官网:
https://www.wolfssl.com/
许可证:
GPLv3 Commercial Licensing  https://www.wolfssl.com/license/

CycloneSSL

官网:
https://www.oryx-embedded.com/cyclone_ssl.html
许可证:
GPLv2
Evaluation License
Commercial License

https://www.oryx-embedded.com/cyclone_ssl_licensing.html

axTLS

官网：

http://axtls.sourceforge.net/index.htm