OpenFalcon is a community build upgrade of Falcon 4, which ports the game engine to modern Operating Systems. The game runs on WinXP Vista and Win7.
Since the moment Hasbro Interactive dissolved Microprose and thus the discontinuance of Falcon 4.0 (patch 1.08) several community build updates were released. Last was SP4 by the Benchmark sims team (BMS). After that, Open Falcon emerged and is continued up until now as a community freeware game which has to be installed over Falcon 4.0.
As Open Falcon sort of organically grew, no release date can be given, because it was leaked before it was ready for a full release. The OF 4.5 and the OF 4.7 releases were just a community's data mod on top of that leaked OF.