According to THIS blogpost, Valve is releasing its Source Filmmaker and Source game engine free to the public.
No details as yet on licensing.
Looks pretty interesting. But I guess it would be very limited to what you can do with it.
Nice more features for me to steal and implement to blender 
I don’t have a good source, but I think I heard the people from the TGS podcast talk about this. Apparantly you are free to use it however you see fit. I think you can even make money of it IF you do not use any of valve’s assets. The film maker will only be available for Team Fortress 2 at first, but they’re going to expand it to accomodate more ( and eventually almost all ) source games.
Well I did some searching and I guess you can find all the answers to your questions here: http://www.sourcefilmmaker.com/faq/
Personally I think it’s great that such a tool now exists but we’re going to see a lot of sh*t ,only a few good ones ( and a single great one once in a while).