VCV Rack has been one of the success stories of the Freemium model, with the basic (we say basic but with 200+ free modules, its anything but that) coming free for Mac/PC/Linux platforms, and additional modules for sale - the premium part of the deal.
Its Eurorack modular environment in software, with integration with your existing audio hardware or software environment making creation of complex patches possible on the computer.
Its proven a fertile spawning ground for new modular ideas and has resulted in some developers launching hardware releases after being proven in software.
Currently still at sub version 1.0, there's going to be multi-core support in the first non beta release (V1.0 we hear), and we can confirm that this doesn't mean it will become a paid product. The original developer Andrew Belt has continued to assure us of this.
But as an essentially open source and well documented platform, its attracting developers to try their hand at this and monetize via premium modules. Thats how Andrew himself supports the project. Additionally, the way the VCVRack installs modules, whether that be free of premium is pretty frictionless for the end user. Many open source of free software requires a lot more technical skill to get things going, but with VCVRack, browse modules, add to your account then download when you launch the app on your chosen platform.
We spoke to developer Martin Lueders (ML Modules) who was manning the booth at Synthfest.