FWIW, it's relevant to OS X too (even Mavericks)...'sudo purge' will reclaim some of the resources.
Linux never needs a 'purge' or equivalent. Doing a 'drop_cache' only slows the system slightly because nothing is cached. 'sudo purge' can prevent OS X from using swap – i.e. running out of RAM even though there is RAM it could reclaim. This behavior has been tweaked but not fixed in Mavericks.
Some small amount of swap usage (compared to total RAM) is perfectly normal, by the way. More cache, for instance, is a better use of RAM than avoiding swap usage by keeping never-accessed pages present.