A bit more details:

- You need an Oculus account but it doesn't have to be linked to your Facebook account, in fact you don't need a Facebook account at all. The exception is Oculus Rooms, a VR social app.

- Obviously there are proprietary drivers. And only Windows 10. I think you can use it in Windows 7 but it is not recommended.

- You don't need the launcher. You can even run bare executables if you wish. The Oculus software still runs in the background though. Also, the Oculus launcher supports "unknown sources", that includes Steam games.

- Oculus have their own store, but you can buy your games elsewhere if you prefer. They have a few good exclusives though.

- Steam games have different levels of support. Some games available on Steam can make use of the Oculus API. These work just as well as native games (because they are) but you may need a command line flag. Games using the SteamVR API also work well, but there may be a few minor issues, like the sound not switching to the headset automatically and a small performance hit. Games that don't officially support the Rift usually work, with maybe a few controller issues.

You need to install the Oculus software to use the Rift, but there is no requirement to have or link to a Facebook account, and afaik, never will be. To run software from outside the Oculus store, you simply go into the Oculus settings and flip a switch enabling external applications.