Last year I wrote a small Perl script to provide a way to use BBEdit’s Find Differences command from the Mac OS X command line. I’ve polished it up a tad, added support for a few command-line options, and released it as a project: bbdiff.
If you don’t use the command line in Mac OS X, bbdiff won’t be of much interest. But if you do, it’s worth a look. While written in Perl, it communicates with BBEdit via AppleScript — it’s a Perl script that runs an AppleScript.
See the bbdiff project page for details. One note: If your copy of BBEdit is not named “BBEdit” (like, say, if it’s named “BBEdit 6.5”), you’ll need to edit the script so that the AppleScript snippet contains the actual name of your BBEdit application. It’d be nice if bbdiff didn’t require you to hard-code the name of your copy of BBEdit, but as far as I know, there’s no simple way for an AppleScript to refer to an appliction by creator code (in BBEdit’s case, “R*ch”) or bundle identifier (“com.barebones.bbedit”). If you know of such a way, please do send me a note.
Of course, you could also simply change the name of your copy of BBEdit to “BBEdit”. The version-number-in-the-application-filename thing is a bit passe.