I really think it behooves proprietary vendors to at a MINIMUM do a source code dump when they decide to sunset a product line/platform.
And while it's nice if you can do it clean, and setup a foundation or donate it to Apache. It's not necessary.
If you can't do those things just toss a tarball over the wall.
If you don't own all the code. Toss the code you do have the rights too.