This isn't altogether uncommon in free software, and is sometimes referred to as 'beggarware'. I've been guilted into donating by some of these, but if it's to

This isn't altogether uncommon in free software, and is sometimes referred to as 'beggarware'. I've been guilted into donating by some of these, but if it's too annoying it can have the opposite effect and cause you to drop the software. One that comes to mind is a download site that tracked your download count and put a rainbow-colored '(maybe you should donate)' link next to it. Not very detrimental to the UX, but gets the message across.