I don't think Larian sold or otherwise lost the right to publish LED Wars, or they would not have bothered attempting to re-compile the game again without the copy protection.
I got the impression it was simply too much work for too little benefit to go through code that they had not looked at in years, track down all the errors due to the differences in compilers, and then have to do a round of beta testing to catch problems or conflicts that didn't result in a compile error.
Presumably the media the original compiler was on got discarded, lost or damaged, or the compiler itself had problems on newer systems.
