“Copyrighten” is an interesting grammatical construction that I’ve never seen before. I’d assume it would come from a second language speaker.
It looks like a mix of “written” and “righted”.
“Copywritten” isn’t a word I’ve ever heard, but it would be a past tense form of “copywriting”, which is usually about writing text for advertisements. It’s a pretty niche concept.
“Copyrighted” is the typical form for works that have copyright.
I’m not a grammar nazi - what’s right & wrong is about what gets used which is why I talk about the “usual” form and not the “correct” form - but “copyrighted” is the clearest way to express that idea.