The Open Source Virtual Reality (OSVR) Project is a very exciting open-source collaboration among some VR companies and developers to bring better interoperability to VR hardware and software. Easier interoperability means faster app and hardware development. The OSVR software framework aims to run on multiple operating systems. In fact the project is continuing Mac OSX development even though Oculus has “paused” mac development for now.
The OSVR team is also interacting with other open-source projects. For example there is an effort to work on an OSVR plugin for the Blender game engine.
The OSVR team has published a roadmap at: http://vrguy.blogspot.com/2015/09/osvr-roadmap-creating-ecosystem-of.html
To keep up on developments, follow the OSVR site and vrguy.blogspot.com.