Corona renderer is a new (un)biased photorealistic renderer, available both as fully integrated 3ds MAX plugin, and a standalone CLI application. While it is still under development, it is already widely used in production. Since Corona was started in 2009 by Ondra Karlík, it became a production-ready renderer capable of creating high quality results, with over 35 000 downloads already.
The renderer is currently in an open alpha-test stage. This means it is free to use, even for commercial projects, without any resolution limitations or watermarks. It can be downloaded at the Corona forum. The forum is currently also the main source of information, since there is no proper website yet.