From today on you can download the F.E.A.R. Multiplayer for free!
Sierra has set up a homepage where you can find several mirrors as well as bittorent links. After downloading the game, you need to register to get a CD-key, which is necessary to play the game online.

Just go the the official homepage and go for the download.

Of course most of the HTTP/FTP mirrors are overloaded, so try the Bittorent-link, maybe you will be lucky and get to play this night.