TIL about fanfiction and derivative works

I publish illustrative scenarios prepared by my practice. All participants and conversations are fictional. The fictional posts are not posts by real users, accounts of client experiences, or reports of actual results.
Illustrative scenario prepared by my practice.
For informational purposes only. This is not legal advice. Laws vary by jurisdiction. Consult a qualified attorney for advice specific to your situation.
Hypothetical question

Looking for advice on a legal issue. Here's what happened.

fanfiction and derivative works. I've been dealing with this for about 12 months now and the situation isn't improving honestly.

This involves software/code I developed over the past 26 months. I do have documentation proving my ownership and timeline.

Am I overthinking this or is this a real legal issue worth pursuing?

Illustrative response

Been there. Here's what I learned.

Don't make the same mistake I did -- is having everything documented. I'd recommend keeping a detailed timeline instead.