IANAL, but I think many patent lawyers would suggest that Bob consider a provisional patent application. This generally much cheaper to draft and file than a full patent application, it gives you an earlier filing date if you decide to go for a full patent, and makes your invention more likely to show up in a prior art search. You'll still have to invest time, and $2,000-$3,000 dollars, but it will probably give Bob some extra protection against someone else patenting his software.

http://inventors.about.com/od/provisionalpatent/a/Provisiona...

http://www.ipwatchdog.com/patent/provisional-patents/