Facebook has yet to release their promised, but long overdue (about 3 months) linux SDK. So about 10 days ago, a group of developers felt compelled to reverse engineer and come up with their own FLOSS version.

Meanwhile, facebooculus is still claiming they will release "soon", and claim to have multiple dedicated developers on it. They have been saying this for weeks. It would be embarrassing, but huge with if a small group of unpaid enthusiast/researchers/hackers beat the facebook team by releasing a working linux (and open source) version.