Merge pull request Mbed-TLS#124 from daverodgman/license-update

Update project license (GPL is back)

Author: gilles-peskine-arm

kb/licensing/how-is-mbedtls-protected.md

@@ -2,9 +2,9 @@
 
 ## Copyright
 
-Mbed TLS (formerly known as PolarSSL) is, like most software, protected by copyright. It is licensed for use under an open-source Apache 2.0 license. The *project* is owned by TrustedFirmware.org, and the code is owned by all the people and companies who have contributed to it, collectively known as *The Mbed TLS Contributors* (except for some files in the 3rdparty directory which have copyright as noted in the file headers).
+Mbed TLS (formerly known as PolarSSL) is, like most software, protected by copyright. It is licensed for use under a dual open-source Apache 2.0 OR GPL 2.0-or-later license. The *project* is owned by TrustedFirmware.org, and the code is owned by all the people and companies who have contributed to it, collectively known as *The Mbed TLS Contributors*. (Note: some files in the 3rdparty directory, not used in the default build, have a different copyright as noted in the file headers, and are licensed under only the Apache 2.0 license).
 
-When contributing code to us, the author is required to sign off all commits with a [Developer Certificate of Origin](../../dco.txt) line, confirming that the code submitted can (legally) become part of the project, and be subject to the same Apache 2.0 license.
+When contributing code to us, the author is required to sign off all commits with a [Developer Certificate of Origin](../../dco.txt) line, confirming that the code submitted can (legally) become part of the project, and be subject to the same Apache 2.0 or GPL 2.0-or-later license.
 
 ## Trademark
 

kb/licensing/using-mbedtls-in-a-non-apache-project.md renamed to kb/licensing/using-mbedtls-in-a-non-apache-or-gpl-project.md

@@ -1,4 +1,4 @@
-# Using Mbed TLS in a non-Apache project
+# Using Mbed TLS in a non-Apache or GPL project
 
 ## Who should read this?
 
@@ -8,8 +8,8 @@ Anyone maintaining a Free Open Source Software (FOSS) project who needs either a
 
 In short: Yes, you can. However, there are a few rules. As a result, a lot of Open Source projects worldwide already use Mbed TLS.
 
-We encourage and support the use of the Mbed TLS library in Open Source projects. You may be able to use Mbed TLS even if your project does not use the Apache 2.0 license itself.
+We encourage and support the use of the Mbed TLS library in Open Source projects. You may be able to use Mbed TLS even if your project does not use the Apache 2.0 or GPL licenses.
 
 ## How does using Mbed TLS in a non-Apache project work?
 
-You should check if the license you use is compatible with the Apache 2.0 license because that might differ by the license type you use.
+You should check if the license you use is compatible with the Apache 2.0 or GPL licenses.