Notch is updated frequently to support new hardware (like NVIDIA’s latest drivers) and features. A crack will lock you into an old, buggy version and prevent you from using the latest real-time technologies.

A node-based visual programming environment widely used for live visuals. The non-commercial version is free.

While not strictly "real-time" in the same way, its EEVEE engine provides incredible real-time viewport rendering for VFX and is completely open-source.

Notch offers a Free Learning Edition . It is fully featured, allowing you to learn the entire workflow, build projects, and experiment with real-time VFX. The only restriction is a watermark on the output and limited resolution, making it perfect for skill-building.