Biab Win should be able to be made to use m4a and aiff as well as wma wav, you need the latest Biab version to install the latest RealTracks and if it's backward compatible it will still decompress your old wma RealTracks.
This will allow the way to have crossplatform installers.
It's a pain also that Biab don't work under Wine because of wma, something needs to be worked out there to allow BiabWin to work under Wine on Linux and Mac. Other audio apps work flawlessly under Wine Biab should be the same. For very little cost you open the market to Linux.