VCV is an open source project of bringing Eurorack experience into the software format. It is already available as application for Mac, Win and Linux. Future updates promise support of VST/AU plugin formats.
Even though it doesn’t feel yet as a finished product - it is pretty nice to try modules before you buy it - it has complete set of Mutable Instruments modules, Befaco and some standard modules.
As it is not yet available as a plugin - it is a bit challenging to use it for music production. You can use virtual cables solutions like Screenflower to hook it up to your DAW. Or use it as a standalone and connect to your Eurorack setup with Eurorack-compatible audio interface like Expert Sleepers ES-8.
Coolest thing in VCV is that they brought digital modules taking the original code of the module (Mutable Instruments modules are open source) and bring those to the virtual Eurorack environment - some of the MI modules sound 100% authentic to me. Braids has same sound as Eurorack, Elements seems to be close too… But I found Clouds not working as expected - it lacks some important controls maybe will be fixed in future versions.
But after all VCV is another nice Eurorack emulation. And for free open source software it definitely offers a lot - great variety of modules that might take hours of playing with. Would be great to see it migrated to iOS some day - such app would be a killer with all the touch-enabled knobs.