In comparison, the Skype native protocol is highly obfuscated binary, so the few reverse-engineering efforts that have surfaced thus far have not revealed all that much. Combine that with the legal issues and it's no wonder a lot of people are still trying to hang onto MSNP for as long as they can with all the unofficial clients out there that support it. On the other hand, from a few sources including the linked blog post (http://messengergeek.wordpress.com/2014/09/11/when-is-messen...) it appears MS is trying to replace the Skype protocol with a newer version of its own MSNP, so it's not all bad.
It looks like MSNP8 is still working, but my guess is that there's something at Microsoft that relies on this protocol which is what has kept it up for so long while some of the newer intermediate versions are no longer supported:
