Choose the right license for a printable

"May I sell prints of this?" is the question every buyer of a 3D file actually has. Printables makes you answer it, and shows your answer above the Buy button rather than in a receipt afterwards.

The choices:
- Personal use only. They print it for themselves. They may not sell prints.
- Commercial use allowed. They print it and sell the prints. They still may not resell or redistribute the file itself.
- CC0 -- public domain. You waive your rights. Anything goes, no credit needed.
- CC BY -- credit required. Anything, including commercial, as long as they credit you.
- CC BY-SA -- credit, share alike. As CC BY, and they release their changes under the same terms.
- CC BY-NC -- credit, non-commercial. They credit you and may not sell prints.
- Custom terms. Write your own. If you pick this and leave the box empty, buyers see a warning telling them to read terms that are not there -- so write them.

If you change the license later, the change gets a new version number. Anyone who was already reading the old terms is asked to read the new ones before the sale completes, and anyone who bought under the old terms keeps the terms they agreed to. That is deliberate: a license you can silently rewrite after a sale is not a license.

The license shows on the buyer's own library page too, so they can go back and check what they are allowed to do long after the purchase.