OTOY offers a version called . It is completely free to use for personal and commercial projects, with a few limitations:

It sounds like you’re looking to get Octane Render up and running in Cinema 4D R25. While it's tempting to look for cracks, they often come with significant risks like malware, system instability, or project-breaking bugs. Instead of a risky crack, 1. The Official "Free Tier" (Prime)

You can't use multiple graphics cards for rendering.

An incredible open-source render engine that is famous for its realistic light handling (caustics).

A fast, production-ready GPU renderer that has a very generous free version for Cinema 4D. Why Avoid Cracks for Render Engines?

It works great with Unity and Unreal Engine, but for Cinema 4D, it usually requires a subscription. However, it's the best way to learn the Octane node system without spending a dime. 2. Student & Trial Versions