Mike,
while the intention matters, you as the developer capable to decompile could be made to think you only help a poor guy saving his business, when he or even hos boss or even higher up the decompiled sources are used to sell the cracked software or do other illegal stuff, eg installing 50 pcs with a single bought license. And when it comes to any investigation you're part of the whole crime.
That's a very pessimistic view, including dmifsud22 might not even be involved in the real intentions, but as said imposters are probably the politest and most thankful people you'll ever meet in your life. And again said, all doubt may be resolved by seeing contract or other paperwork proving the ownership. Since this is old software and the developer was involved personally I assume there is paperwork, otherwise communication, mails. In case the final license was bought only you might only have mails about that purchase, but also some money transfer would proove at least the ownership of the license.
Maybe I'm overreacting and being overcautious here, but that's the way it is.
Bye, Olaf.