As the copyright owner you can do whatever you want. You can make your code gpl and give (written) permission to only blizzard to use the code under a different license.
You’d need a CLA for potential contributors though and I have no idea what courts think about it (not a lawyer, not legal advice).
For the Index and 2.0 Basestation it’s supposed to work for a while now https://github.com/ValveSoftware/SteamVR-for-Linux/issues/320#issuecomment-1835581128