Yeah, it's actually three, though only from a branding perspective. They did rebrand Lync/Office Communicator as "Skype for Business" for a bit, though I don't

Yeah, it's actually three, though only from a branding perspective. They did rebrand Lync/Office Communicator as "Skype for Business" for a bit, though I don't think there was ever any code shared and it was just a branding thing. Honestly I think they simply don't care, and from their perspective they finally have gotten it right with Teams.