Got my hands on a copy of SAM Broadcaster 2015.1 this morning despite Spacial trying to obfuscate the download links.
The changes list reads like this:
v2015.1 (1 June 2015)
* M4A support added.
* Check SAM Broadcaster edition and warn if overwriting a different edition
* Warn/disable when there is no support for WMA
Last updated on: 22nd March 2018
at 15:50 PM Europe/London