Before y'all get excited, the press release doesn't actually mention the term "open source" anywhere.
Winamp will open up its code for the player used on Windows, enabling the entire community to participate in its development. This is an invitation to global collaboration, where developers worldwide can contribute their expertise, ideas, and passion to help this iconic software evolve.
This, to me, reads like it's going to be a "source available" model, perhaps released under some sort of a Contributor License Agreement (CLA). So, best to hold off any celebrations until we see the actual license.
I would argue that even having a project as source available is better then closed source and can still be pretty good, look at for example the FreeSpace 2 Source Code Project.
If anybody want to ask a game creator to make a game open source and he refuses, suggesting a source available license might still be a good idea.
But how does source-available benefit anybody? If you get inspiration from the code you can get accused of copyright infringement so you're better off never looking at it, and since it's not actually FOSS you don't get any of the usual benefits.
If it was source available under a CLA, would it make sense for them to specify that they will retain control over the "official version" of the software? That would seem to imply they will not have control over unofficial versions, presumably differently-named forks.
Winamp will remain the owner of the software and will decide on the innovations made in the official version," explains Alexandre Saboundjian, CEO of Winamp.
Maybe the old Winamp goes OpenSource, like the old MS DOS. But certainly not the current or last version. Anyway there are several way better FOSS alternatives to Winamp. It's not a big problem for MS or any other company to release the source of an outdated version which anymore create incommings. In GitHub they still can control Winamp.
There are winamp clones on Linux, have been since the 90s, and they work with the Minus sound systems. Nobody will care about the actual Winamp (which doesn't).