Estimated development cost: . Market size: extremely small (retro MIDI enthusiasts, game composers from the 1990s). Hence, no commercial entity has done it.
Is it official? No. But it's stable, lightweight (under 6MB), and legally ambiguous—though Yamaha has not issued takedowns, likely due to the age of the technology and the fact that the original ROM data is not redistributed (the plugin reads your legally owned S-YXG50 .SYX or .TBL files). yamaha xg vst 64 bit new
There have been in the last two years: