[throwawaykf02]

I'm on a mobile device, so I cannot research as much as I'd like, but this is just a patent application, not an issued patent, and more encouragingly, a quick glance at USPTO pair shows that is was abandoned in 2010. It was abandoned following a non-final rejection by the examiner.

Now it doesn't mean that it's dead for good, since abandoned applications can often be revived, but given that it's Microsoft, who has enough resources to pursue even trivial patents, and that it has been 3 years since it was abandoned, I'd be cautiously optimistic.

On the other hand, it has been referenced by a bunch of other patents, indicating they cover similar subject matter, so you should look into them too.

PS being open source won't save you from infringement.