I don't see issue. 25 years sounds entirely reasonable copy right protection period for software. Meaning that you can freely sell 25 year old versions of software. If you haven't upgraded or released new versions under new term, you really don't deserve protections. Sell version 1 in 1995, it would be now free. On other hand the version 2 with more features as non-free upgrade released in 2000 would still have some protections left.

Trademarks are also different from copyright. It gets complicated, but you shouldn't be able to do confusing things with them.