Last year, Take-Two mentioned when they renewed the Houser brother's contract along with other key members of Rockstar that the Housers and other key members of Rockstar were founding a separate video game company and that Take-Two would not own the company but would have an publishing agreement with the company. Today, Variety posted an article about an announcement for the company but before I could read it the article was pulled from the site. However, an RSS syndicate blog posted a brief preview of the article that mentions that the company will be named 4mm Games. The summary also mentions "...[4mm] hopes to reinvent the roll out of new titles using the Web".  By that it would imply that they are creating a Steam rival. On the other hand, I looked at the official website for the company and it says their focus is "developing online worlds that will define social gaming", which to me implies that they are working on a MMO of some sort. So at the moment, it's not totally clear yet of the focus of the company.The company has a mailing list sign up in the about section. Perhaps we'll hear something soon.

Official Website: 4mm Games
Source: Variety via Movienet

EDIT: It seems I was right about them doing a MMO. After doing more research, I found a video by Jamie King that explains the aim of the company a lot better.

EDIT 2: For anyone worried about Rockstar, don't be. No one is leaving Rockstar, not even the Houser brothers. This is more of a side project for the Housers. The day to day operations of 4mm are under the control of Jamie King who left Rockstar back in 2006 to be at 4mm full time. The title won't be Take-Two funded or even a Take-Two owned IP as Take-Two is merely just a publishing partner. It remains to be seen if Take-Two decides to publish the title under the Rockstar brand. Kinda like Prey which was owned and developed by seperate companies, but with Take-Two as the publisher which decided to publish Prey under it's 2K label. We're betting it will be.

Edit 3: When I read the contract renewal announcement from Take-Two, I assumed the Housers were involved with 4mm Games. The Variety article has since came back online and explains that Jamie King and Gary Foreman are the only two from Rockstar at the company. I apologize for making that mistake. However, just like I stated in edit 2, Rockstar is still not affected in anyway.