To avoid further confusion, it is allowed to ask for donations as long as they’re given away and not kept for yourself
Link to OPDonations
You can't force users to donate when they are adopting. Donations must be optional, or else your topic belongs in the trade boards, since your pets/items aren't really free to adopt.
You may not have special pets or items or a special group of pets available only to users who donate.
If you're taking donations, you must be willing to accept all unwanted pets/items. You can't only request certain outcomes, species, or rarity.
Any donations received must be given away for free in your adoption topic. You can't trade donations for any reason or keep any donations for your own personal collection.