Just got a question from a customer how to download Skype for Business for MAC?
2016-02-18: According to this blog posting here its planed for 2016 but not yet released. According to the information we got the mobile clients will be upgrade before the Skype for Business for MAC will be released. As the Android and iOS client is updated that should not take that long now.
Update (2016-10-28): SfB for the MAC can now be downloaded here.