Certainly take your point about free games getting less downloads than paid for games, however, we haven't really looked at that data and there is this odd situation where when things are "free" they are sometimes seen as not worth bothering about. It might also be that those charging for their games are confident that they will sell and their research is right?
As for large software houses, ideas are often copied and recopied over and over, sometimes intentionally, sometimes unintentionally. Of course if they were to use the actual resources of a game then we suspect there would be (or maybe that should read "hope there would be") some consequences either financially or by way of reputation being damaged. One would hope that if the resources of our game were used by a large software house, or the idea (which came from a short story written 11 years ago by one of us, and published online) were stolen, it would look pretty awful that they had essentially stolen from young people who were making a game for fun.