Editing existing modules

I’m new to VASSAL and I tried playing Middle Earth Quest.
I noticed that it is hard to keep track of the number of cards in your decks and that some cards from a different deck (skill cards) are not fitting into a new deck when moved there (meaning, they lack commands to move them to certain decks).

So I added an option to choose the hero that receives the skill card, so those cards can be sent only to that hero’s decks.
I also added the number of cards in the rest/life/damage pools for the heroes.

I know it’s not hard to do, but it makes it so much easier while playing.
Who is allowed to contribute to the modules of VASSAL?
If I want to create a newer version of a module, am I allowed to do that?

The way I understand it, the general rule of thumb is to make an effort to contact the original module designer and work it out with them. The module pages will usually have a Maintainer / Contributor. If you log into the module wiki (this is a separate login than the forum), these names will usually give you E-mail links …if they’ve provided them.

If, over a reasonable period of time, you can’t contact them, then consider yourself free to modify / create at will. Just make sure you give credit to the original developers in the comments and don’t remove their versions.