I'm happy to find this being maintained again because I really don't want to learn python just to customize Gimp. However, it was difficult to install because the prerequisites are not given (that I could find) in the POD, and the README from the tarball does not give a complete list. YMMV, but this is what I did before it would install on Linux Mint 17.1:
Verify Gimp 2.8 and Perl 5.14 or higher.
Install libgimp2.0-dev (it wasn't installed with Gimp).
Install the following modules from cpan:
Once I figured out all of the prerequisites, this module installed without a problem. Hopefully this info will save someone else a few painful hours.
This was just too easy. The module makes implementing captcha trivial, plus you'll also get karma points for helping digitize books. The most difficult part was reading the terms of service when registering for a reCaptcha account.