On October 27, 2016, Microsoft made the all new Skype for Business on Mac client generally available for download. With this client now available, The Skype team has provided modern clients on all t...
Updated Oct 27, 2016
Version 4.0
Blog Post
Thank you Dale Christian for the question...and to Chermaine Li for the answer:
You can go to the Microsoft Auto Update prompt and de-select the checkbox to Join Office Insider program: https://support.microsoft.com/en-us/kb/3136076.
Q. How does a user opt out of the Insider program?
A: The first step is to clear the Insider check box. However, this affects only future build update notifications and does not revert the software that’s currently installed. For Office Insider Slow, since the non-Production build is run only for approximately seven (7) days each month before upgrading to the Production build, it’s likely that users will already be running the same build as the Production channel. However, if users have recently installed an Office Insider Slow build and have to revert to the earlier Production release, they will have to remove the build and download and install an older update. For Office Insider Fast, it may take over a month to receive the next Production release due to being one version ahead of Office Insider Slow and Production during a given month. Thus, users will have to remove the build and download and install an older update. MacAdmins is a good resource for finding older releases.