You can read the details here. They don’t explicitly say that it is dead, but, basically, it is.
From a product placement perspective, this makes a lot of sense (then again, I’m hopped up on cold medicine, so judgment might be sketchy right now). From a developer perspective, this kind of sucks. I have a major project that uses it, so it is rather annoying. Since I have my entity layer sit on top of my Linq to SQL data layer (which frankly everyone should have been doing anyway already), it’s an easier path for me to migrate to EF or NHibernate or whatever, but it is still annoying.
I think the likelihood that Linq to SQL will make it to open source status is pretty remote, so I wouldn’t plan on that becoming a reality.