Why do I see 4 (or more) copies of named on Linux?

Linux threads each show up as a process under ps. The usual set of threads running is the main thread, a socket reading thread, a timer handling thread, and multiple worker threads, where the number of worker threads defaults to one fewer than the number of CPU cores available (minimum one). Note that the amount of memory used is not cumulative; if each process is using 10M of memory, only a total of 10M is used.

Newer versions of Linux's ps command hide the individual threads and require '-L' (or 'H' if using BSD style flags) to display them.