You might be more familiar with this than I am, but I thought BMS was supposed to be stand-alone. Heck, most of the user-maintained versions of Falcon are stand-alone!
I've played with FreeFalcon a bit, but not too much. As far as I know, most flavors of Falcon are a tad bit buggy and require some finagling to make run properly. The main focus of FreeFalcon is to be more stable, and so far as I know, does better in this department than BMS. FreeFalcon has not been made to delve as much into further developing the realism of the F-16 as BMS has, but it will allow you to fly pretty much any fixed-wing aircraft it has in its database. I believe that both the BMS and FF communities will strive to work with each other more in the future, so hopefully, we'll get the best of both worlds.
...More importantly, if we get a sim that doesn't need to be re-started every new mission (during campaign), or a sim that doesn't need to have the user jump through hoops to manage properly in general, then it will be a good day indeed!