Copyright has a limited term. For many works created on or after January 1, 1978, it generally lasts for the author’s life plus 70 years. Works made for hire and certain anonymous or pseudonymous works generally have a term of 95 years from first publication or 120 years from creation, whichever expires first. Older works and special circumstances require separate analysis. See 17 U.S.C. § 302.
Transfers, licenses, and other agreements also affect what a rights holder may do. Before signing a broad grant, consider exclusivity, duration, permitted uses, sublicensing, and termination. Ownership of a physical copy is different from ownership of the copyright.
If another party is using your material, preserve the relevant records and obtain advice about ownership, permissions, defenses, and available options. A copyright dispute should not be assessed from a screenshot or similarity alone.