This was done to clean up the license and to ensure that any commercial fork of the engine has to obey the far stricter requirements concerning source distribution. The old license was compatible with GPLv2 whereas combining GPLv2 and LGPLv3 force a license upgrade to GPLv3. The license of code that originates from ZDoomGL has not been changed.
That's again one less write access to the buffer. The uniform method was chosen because this way a buffer update can be completely avoided, and setting a single uniform is a lot cheaper and simpler to handle.
Added gl_renderbuffers CVAR that disables render buffers
Added patch shader support to FShaderProgram
Added OpenGL 2 fallback support to render buffers
