If you’re looking for RegexKitLite 3.3, it’s a little less than intuitive to find it. I eventually found it here after just grabbing the URL for the 4.0 release and changing it to 3.3.

Why would you want an older version? According this this post on the Cocoa Dev mailing list apps have been rejected for using RegexKitLite 4.0. You can either replace your 4.0 version with 3.3, or just add the -DRKL_BLOCKS=0 flag to your OTHER_CFLAGS build settings in Xcode (much simpler in my opinion).