So, a notice in the manual and a git repo is reasonable.

I sort of wonder what is unreasonable

Suppose you wanted to be evil - and require communication via fax machine charge processing fees and postage to send the source on a series of floppy disks.

Or to not notify in the manual, but rather have a QR code with text or a link, or no QR code and just have a long legal disclaimer document on a website that they magically need to know exists, or something

Do any good examples of unreasonable-ness exist in this context? I can only think of a very few examples that got any publicity.