I don't really use these games databases, but I'm aware of some of them. Some of them are no longer maintained, and those are getting out of date. One database that's currently maintained is MillionBase 2017. (Thank you, Ed Schröder!) It's not the biggest database, but at least it's fairly current (as of end of 2017). Unfortunately, it's only in PGN format, so you might have to convert it to another format like Scid.
http://rebel13.nl/download/pgn.html
I guess I'm a bit confused about baddogno's post. Are you wanting a games database that you can download and use in a standalone fashion on your home PC using something like the Scid GUI? If so, I can't believe that that would violate any site rules. I mean, people discuss these games databases all the time in the "Books and Equipment" forum.