It’s a nice thought, just extremely unlikely, no? Unlikely that someone has the time to deal with a huge legacy system, and unlikely they’ll be able to rewrite portions and get it working. There are very good reasons this hardly ever happens, releasing proprietary code, even when it’s all modern and working. The potential downsides are usually bigger than the upsides.

It has happened with OpenJDK, first downstream with the IcedTea distribution, and then gradually things were replaced upstream or opened by Oracle. I think today, only the browser plugin is missing, and nobody really wants that anymore.

It's rare that this happens in the open like this. I expect that it was a factor that OpenJDK was a free software development tool, so Sun already had transferrable licenses from their suppliers. For other types of software, building new software with it is not a consideration from the outset, and licensing agreements with third-party component suppliers will reflect that.