Supersound.dll is said to be published by GOG.com according to a website I was reading. I think I may want to use it in an indie game I'm making. If GOG.com did publish it, is it free to use in commercial projects, and does it require attribution in credits? Is there some good documentation on how to use it (the commands it takes, or use examples) that you could refer me to?

I have an ugly surprise for you; Supersound.dll wasn't made by GOG.

It's just a GameMaker library that allows the playback of OGG and WAV files, so it's basically a hack for a game making engine that can't even manage to support that.

(source)

So I guess the info was incorrect. Here's the source.

http://windowsbulletin.com/files/dll/gog-com/spelunky/supersound-dll

Look under What is supersound.dll if you want to find it.

I know it's something for GameMaker. GM supports sound I just want the system to work better in this specific area. I guess it's probably free to use if an amateur coder made and distributed it. Does GOG.com publish any dlls at all by the way?

Since the URL states Spelunky (the game) it's probly signed by GOG. Anyway, scroll down in that page amd check the comments.