Why donate when it's free?
If you enjoy zooming around the solar system in your spacecraft, spare a thought for the effort that has gone into developing Orbiter. Writing a spaceflight simulator is a lot of fun - but it's also hard work, with long nights spent on design, coding, testing and debugging. Orbiter is purely a hobby project, so funds for equipment and infrastructure are very limited.
If you like Orbiter, you can show your appreciation by making a donation. Donations help pay for hardware and servers, and they make it easier for me to justify spending even more time on developing new features and keeping Orbiter going for another release.