If the product is dead, that means the licencors are likely to no longer make any money off it it. This means they will likely be open to open sourcing the code for free or next to free.
Open sourcing dead projects do have advantages for the licencors:
1. nobody likes the code they worked hard on to be dead
2. it's valuable free marketing for their brand name
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.
Open sourcing yes, but what about just "opening the source" aka a source dump with no rights given?
I can't see myself using the source for anything, especially since all browsers are dropping support for plugins. But I'd really want to see if the source is so bad that they couldn't fix the issues (crashs, battery usage), or if it died due to political reasons.
