vkon: it is completely useless, and counterproducent.

Honest people (the Client$) that could benefit from taking a look at the source code won't be able to do that. But then again, they wouldn't (being honest and all) redistribute your program, either, nor modify it (if you stated that they are not allowed to). The Client$ lose, you lose.

Dishonest people will disassemble it, recover the (even if somewhat obfuscated) source, and do as they please. The bad guy win, you lose.

So, (IMHO of course) there is absolutely no sensible reason to obfuscate your source code, unless if it's so ugly that you are ashamed of it.

WRT good argument for lawyers: a good, explicit copyright license (even a restrictive one) is a better argument for lawyers than source code obfuscation. Something like:

(C) 2008 MassaCorp
This is proprietary and confidential information
you received from MassaCorp. This program can be
run by The Client$ Corp on its computers A, B and
C, but all other rights are reserved. Particularly,
no copies at all can be done without MassaCorp's
explicit, written, authorization, and no
modifications can be done to this program
by anyone that is not an authorized MassaCorp
technician. Any warranties not present in your
maintenance contract are null and void.
[download]

does everything an obfuscation scheme does protection-wise, and opens the door for litigating (your own clients?! think SCO) if necessary. You can even watermark versions of the source code (randomly change some $h->{a} with $$h{a} and log which changes went to which client) to find bad-faith people.