They’ve taken a step back from recreating specific synths and are emulating the Motorola DSP56300 chip, used in classic mid-’90s and early noughties instruments such as the Access Virus, Clavia Nord Lead 3, Waldorf Q, Microwave II, Novation Supernova and many more.
You can think of this as being similar to the multitude of video game emulators that are out there, which don’t actually do anything until you provide a hardware ROM. And this is where it gets a little murky; while the emulator itself is not illegal, the sharing of ROMs most definitely is.
The DSP56300 developers say that they’re planning to release a VST/AU plugin version of the emulator at some point in the future.
When this might arrive is hard to say - the project is being worked on in people’s spare time - but a primitive version of the emulator, with no GUI, can already be downloaded. This can be controlled using either VirusHC or Ctrlr, and you’ll need a virtual MIDI cable.
Find out more on the DSP56300 emulation blog.