"Skype: patched and recompiled to do other stuff" is a better title. Decompiling a proprietary product, changing a few lines of code, and then releasing that code doesn't make it "open source", it makes it stolen code (semantics of "piracy is not theft" aside, it's still not his code to be releasing in it's entirety.).

You are wrong. Decompiling is just allowing research deeper in skype-black-box. Project itself is here https://github.com/skypeopensource/epycs

If you want to stay within the law my understanding is that you need to distribute patches against decompiled Skype rather than decompiled Skype with patches applied, otherwise you're distributing a derivative work. This may still be a legal grey area though. IANAL, you ANAL, we all ANAL and that.

The name falls under trademark protection and is not related to copyright.