This comment about email client monoculture made me wonder if what the poster is describing is possible.
Say I write and distribute a piece of communications software, like Outlook or Trillian or one of those new-fangled apps for posting on different Mastodon servers. Can I impose a licensing obligation on my users, like "you must give the recipients of your message a license to copy it"?
Or, perhaps equivalently, imagine a version of Photoshop that always produces CC-BY images, because the user is obligated to attach those terms to the output.
If so, how would I do that? If not, why not?