If anyone interested, here is the RUnit 1.3 modified for NUnit 2.4.2:

http://blogs.byte-force.com/files/folders/runit/default.aspx 

Available sources and binaries build for .NET Framework 2.0.

I hadn't time to test this code enough. Looks like there is a problem with coloring of executed tests there - no green or red balls. Not sure there to look for it, most likely in the visitor class.