LOOL Spoiler And starting this month, the PhysX SDK is available free with full source code for Windows, Linux, OSx and Android on https://github.com/NVIDIAGameWorks/PhysX.
ah figured it out... you have to join gameworks on nvidia dev site and give them your github user name to get access to nvidia github. then go to git hub and login and click on nvidia invitation to gameworks
Well, Unreal engine wouldn't be able to go full open source otherwise. It would have to be just parts of it. Unity also has some open source parts.