If you're using a service hosted by someone else, then it doesn't matter if it's open source; you're using someone else's closed environment. In that case you're just as well off using Google or Microsoft. Probably better off, since they aren't aren't hosting on a shoestring budget.
The point to having it open is so that you can host it yourself and modify it yourself.
The point to having it open is so that you can host it yourself and modify it yourself.