AndyD wrote:as I understand it Rotor is the .Net CLI on FreeBSD,
From what I gather, Rotor doesn't have anything to do with FreeBSD, necessarily.
Rotor is a free, shared-source implementation of the standards and specifications that the .NET Framework also implements. Currently it can be built for Windows or FreeBSD, but the point is to have an open version of the .NET standards available for people to study and learn. It can't be used for most commercial purposes (like writing a CLR for OSX). Most people whom I see interested in Rotor get into it to better understand .NET - and therefore write programs that work better with .NET, like adding new .NET-compatible languages and such.
Rotor, I am given to understand, is NOT production-quality code. It has not been optimized for speed, and probably not been tightened for security. It's a learning aid more than anything else.