[mbed-tls] Mbed TLS license change

Hi Mbed TLS users,

We are planning to change the license for Mbed TLS shortly, from Apache 2.0 to a dual license Apache 2.0 / GPLv2-0-or-later license.

This will allow GPL-licensed projects to take Mbed TLS under a GPL license.

Projects which currently take Mbed TLS under an Apache 2.0 license may continue to do so, and therefore should not be affected by this change.

The inbound license, under which we accept contributions, is already a dual-license. There is therefore no impact for contributors, and no impact on PRs that are currently in review, or those that have previously been integrated into the library.

We hope that this will enable more projects to make use of Mbed TLS.

Dave Rodgman