is node.js a one process server, or can it emulate Apache bunch of child processes, each serves a different request, and each is independent from the other (and the cycling of child processes to avoid long term memory leaks).
Is it at all needed when using node.js?
Node.js by default is a one process server. For most purposes that's all that's needed (IO limits and memory limits are typically reached before CPU limits).
If you need more processes you can use http://learnboost.github.com/cluster/