MacOS
kJams is fully functional on Mavericks!
There are some Caveats, however.
If you use a separate display for your Video, you'll notice you now have an obtrusive Menu Bar on the Video screen, even if you go "Full Screen". Super annoying, i know.
You can get around this by going to Preferences->General, and Checking the box that says:
Video window floats above all system windows (When Full Screen)
WARNING: If you check this box, it is POSSIBLE, however unlikely, that a system dialog box will open UNDERNEATH the Video window (eg: an alert dialog, the open/save dialog, a "can't eject" dialog, or any number of other, really important dialogs). The problem is you'll never know this dialog came up, because it's hidden under the Video window.
So if you find kJams or your machine hanging and you don't know why, click in the Video window to get out of Full Screen mode, and see if there's a dialog looking for some input!
Playing KMA, WMA, WMV files
Previously you could use an older version of Flip4Mac, that was free. However with Mavericks you MUST use version 3 which is NOT free.