FIRST, NOBODY WILL EVER BE REQUIRED TO CONTRIBUTE MONEY TO PLAY X-WING ON VASSAL.
Become a patron for the module
If you want to help support the effort of building up the module which involves a few people led by Mu0n, consider pledging a donation each time a major module update is released. For the full details about how you can also enter ship raffle (if the pledge level becomes high enough, go visit the Patreon page.
However, if you prefer to make a one-time donation, consider sending what you like using this paypal me donation link.