Well all he has to do is remove the word "donation" from oQ and put a link to his website with the donation there. I believe there are quite a few addons that are donation-ware (carbonite? I don't remember).
From what I read in the thread on the official forum, oQ is actually costing the author money because he has to run a few wow accounts to keep the mesh and the scorekeepers up 24/7 in all regions (and of course the PCs and higher electricity bills, etc... ) so it's only fair that he put up an >optionnal< donation system, the addon being free.
Personnaly I probably would'nt play wow anymore without oQ. I'm on a now dead server with irl friends and oQ is the only way to do flex, RBG, worldbosses consistently every day/week.