There is nothing to stop you from running 16 copies of AFNI at once. But I'm not sure it would be useful for any purpose. What is it that you want to accomplish? Never having used a Beowulf cluster, I'm not sure of the mechanics of starting processes that are locked to a specific node.
The only parallelized parts of the AFNI package at present are 3dDeconvolve and 3dNLfim. These programs can take advantage of multiple CPUs, but only with an SMP system -- the child processes are created via fork() and communicate via SysV IPC shared memory.
bob cox
