I was thinking about getting one of these too, since I have a bunch of magazines already. I then did some reading up on the whole thing since I could not find any company that had made a viable product with FAL mags. From what I have been able to gather, and it makes sense, is that the FAL has the feed mechanics built into the rifle, not the magazine. There have also been issues due to the way the magazine is designed to lockup.
As for others... well DPMS and KAC make them, and they use the SR-25 magazines. Then there is Armalite, which uses either modified M1A mags, or more recently their own design. One last one is COBB manufacturing, and I believe it uses the G3 mags (which are good mags, and cheaper than FAL ones currently).