I think it's entirely up to the author. If you're proud of it or you're doing something clever or unusual and you think others could learn from it, then by all means share the source code. If you're embarrassed by it or your source code is a mess or you're worried about someone ripping it off, it's probably better that you don't share it.
Remember that Adventuron source code may only compile for the version of Adventuron that it was written for, due to all the ongoing changes, hidden features and experimental stuff that a lot of us rely on. So, make sure you state the expected version of Adventuron somewhere.
I am currently rewriting some of my old games and you'd be amazed at the amount of re-engineering required.