"I'm Not A Lawyer," But ...™
You will need to be able to show that the work is
yours; that it's not "a work made for hire" and that you did not make it while employed by anyone else.
If you can show that, then I would recommend that you secure a copyright to it in your country, e.g.
it would cost about $35 bucks. Once the certificate comes in the mail, you're now free to do with "your property" anything that you like ... including give it away.
Now, the copyright office just registers
your claim. They do not validate it. However, this is
a legally definable declaration of claim that is internationally recognized, and it's something that I would definitely require from anyone who offered me anything. My butt, basically, is now covered: if someone sues, I can point to this certificate, which I kept a copy of and which anyone can look up, and truthfully assert an innocent-infringement defense. (Meanwhile, your
butt is toast.)