Out of frustration, I've created a small package that includes the Guifications plugin for Portable Gaim 1.5 -- it's available here, and the MD5 checksum is: 90666fbd3fc169a236661c13f28f71d7
Simply extract the contents of this 7-Zip archive on top of the existing directories underneath ./gaim. You can grab additional Guifications themes here.
Enjoy!