Zetaboards was my favorite free online forum tool (do you call it software if you didn't download it ). I loved how easy it was to use and a lot of forums used it. It also looked very nice.
I spent over 13 years on InvisionFree and later on ZetaBoards. ZetaBoards was definitely ahead of its time. Perhaps not in pure development terms, but the community, resources, and talent it contained were unmatched anywhere else. It was a sad day when Brandon announced he was selling the platform. Part of me still holds him responsible for that decision.