Overload is not an indie game, not in the typical sense anyways. Overload was developed by two of the original master programmers of the original Descent, Mike Kulas and Matt Toschlog.
https://en.wikipedia.org/wiki/Volition_(company)
I also have a copy of Overload, and have played it. It's not an indie game, it's the true spiritual successor to Descent, by the lead original developers.