Source : Free On-Line Dictionary of Computing

Use the Source Luke
     
         (UTSL) (A pun on Obi-Wan Kenobi's "Use
        the Force, Luke!" in "Star Wars") A more polite version of
        {RTFS}.  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 licence}.  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}.  {FreeBSD}, {NetBSD},
        {386BSD}, {jolix} also have their followers.  Cheap commercial
        Unix implementations with source such as {BSD/OS} from {BSDI}
        are accelerating this trend.
     
        (1996-01-02)