OpenMOSIX and Beowulf are only similar in that they are clusters. Nothing else.

Beowulf is a computing cluster that uses standard cluster APIs such as MPI; you need specially compiled code to run the code against the Beowulf. Beowulf clusters would be used in traditional computing clusters: climate analysis, weather prediction, etc.

OpenMOSIX is more of a "load-balancing" cluster (bad word.... but never mind). Programs do not have to be specially compiled for running on the cluster, and the cluster moves each program to a particular computer in the cluster, taking advantage of speed and low system load.

They are for different purposes. I don't think Knoppix would be useful in a Beowulf cluster - but for use in an OpenMOSIX cluster it just might be ideal....