Flip4Mac and QT Pro won't help. They do video.
If you want free, take those WMAs to a peecee with iTunes, then
burn to CD. That'll put them in AIFF format, from which you can
convert to any other Mac-friendly format.
Otherwise, it's at least $10 (EasyWMA, Sound Converter). More $
will get more horsepower. I'm fond of Switch.