I probably doesn't understands everything and you probably have more knowledge than me on that but as far as I understands that's more a standard that a library

I probably doesn't understands everything and you probably have more knowledge than me on that but as far as I understands that's more a standard that a library. You still need to write the actual drivers for your headset and as far as I know, the one for the Vive isn't opensource. OpenVR is still open, it's just the Vive drivers that are not.