Not necessarily. It means that Llama group, and perhaps the original Nullsoft, have violated the license of whatever open source developer wrote that code originally. So the only ones who could actually go after them to force anything are the ones who originally wrote that GPL code. They would basically have to sue Llama group, and they might also have a case against Nullsoft / AOL (who bought Nullsoft) for unjust enrichment over the years Winamp was popular.

Chances are it would get settled out of court, they would basically get paid a couple thousand bucks to go away. Even if they did have a legal resources to take it all the way to a trial, it is unlikely the end result would be compelling a GPL release of all of the Winamp source. Would be entertaining to see them try though.

Complicating that however, is the fact that if it's a common open source library that was included, there may be dozens of 'authors' and it would take many or all of them to agree to any sort of settlement.