Maybe, maybe not. My own completely amateur non-lawyerly belief is
that the deschall code could be legally exported. It's not really an
encryption engine. The problem is you'd have to be brave to export it
without getting prior approval first. And that prior approval is a
real pain in the ass.
As for whether Java DES cracking is a good idea, the main answer is
it's going to be very very slow. The code you're running on your Intel
hardware has been heavily hacked in assembly. No JIT available now can
do that.
>Wouldn't this idea sincerely annoy the person whose machine actually found
>the key, if they ever figured it out?
They don't need to ever know. If you're going to go ahead and run
unauthorized programs on someone's machine, then you might as well not
tell them if their machine actually found the key.