modul multiple games?

When I buy a module, can I use it for multiple games? because I plan to play the DND Dragon Campaign with two groups

When you purchase something from the marketplace, it can be used as many times as you want. There are no limitations on how many games a module can be used to create, how many games an addon can be added to, how many times a token can be pulled in games.

ah thank you for this fast answer

It is no problem. That question gets asked occasionally and Roll20 tries to treat it as if you have it at your table. If you buy a module at a shop, you can use it in as many games as you want and they try to replicate that on the site when you purchase something here. The only downside is that modules, addons, and some graphic packages are restricted to Roll20 but most token and tile packages can be downloaded and used elsewhere.

Oh, remember that anything you purchase on Roll20 is tied directly to your account and it's subscription level. This means that if a friend creates a game, you won't be able to use any addons, any modules that you purchased, or most tokens/tiles (you would have to be a co-GM to use tokens you purchased, I think) in/for their game. You would have to be the one to do the heavy lifting and create the game but you could then bump them up to co-GM for that game and let 'em do their thing.