Earlier this year in July, Valve announced its plans to release a function version of Steam for the Linux.
The team started with Ubuntu and a Left for Dead 2 port and started the beta phase in October with invitation going out to a thousand users.
Valve is progressing in the beta phase and now plans to invite 5,000 more users to test it out,
“We’re making good progress finding and fixing issues that our users have reported so we’re expanding the beta by 5000 before the long holiday (US) weekend kicks in. New limited beta testers will have an email notification in their inbox.”