UTSL

UTSL // n.  [UNIX] On-line acronym for `Use the Source, Luke' (a
   pun on Obi-Wan Kenobi's "Use the Force, Luke!" in "Star
   Wars") -- analogous to {RTFS} (sense 1), but more polite.  This
   is a common way of suggesting that someone would be better off
   reading the source code that supports whatever feature is causing
   confusion, rather than making yet another futile pass through the
   manuals, or broadcasting questions on Usenet that haven't attracted
   {wizard}s to answer them.

   Once upon a time in {elder days}, everyone running UNIX had
   source.  After 1978, AT&T's policy tightened up, so this
   objurgation was in theory appropriately directed only at associates
   of some outfit with a UNIX source license.  In practice, bootlegs
   of UNIX source code (made precisely for reference purposes) were so
   ubiquitous that one could utter it at almost anyone on the network
   without concern.

   Nowadays, free UNIX clones are becoming common enough that almost
   anyone can read source legally.  The most widely distributed is
   probably Linux, with variants of the NET/2 and 4.4BSD distributions
   running second.  Cheap commercial UNIXes with source such as
   BSD/386 are accelerating this trend.