Licensing and stuff

Are there any rules about posting modules? Does the game manufacturer have to approve in advance. As it is, you could download a module and play a game you don't own. That, I would think, would cause game manufacturers to get concerned. I found a Vassal module to Memoir44 on another site, and I have been working on modules for Carcassone and Trias. I wouldn't mind posting them, but I don't need problems. Any advice?