This server allows people to help cover the costs of running this server. There are no rewards for doing so, it really is a donation in the traditional sense.
You can do donations in several ways, one-time donations are possible, although regular recurrent (e.g. monthly) donations are preferred. Donations are possible via bitcoin, paypal, SEPA, and any other method that may be practical.
If you'd like to donate, ask in chat about who you need to talk to/what the email address is.