Flash player might be dead, but that doesn't mean $THIRD_PARTY_LIBRARY that it uses isn't still being profitably licensed by its original developers. Or maybe the player uses a library that Adobe have a perpetual binary license to, but the original company that owned that library went bust a decade ago and nobody knows who owns the copyright on it now to allow a relicense. Open sourcing things does have a cost, and a big chunk of that is in running down these legalities.