An indie developer is an individual, small group, or small independent company that is not owned by another company that makes games. Indie game developers generally do not have the financial backing of video game publishers. Being independent means indie developers, like Michael Scott at Quest Arts Interactive, do not require publisher approval for key decisions as many mainstream developers do. This means Quest Arts Interactive does not have any controlling interest that can restrict creativity or experimentation.
So, what is an indie game? It's a game where the game makers pour all of their love and creativity to make something interesting and meaningful that includes their personal touches. They did not have to make any compromises for anyone.