RegexKit 0.6 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software. The program belongs to Developer Tools.
From the developer:
RegexKit is an Objective-C framework for regular expressions: Support for Mac OS X Cocoa and GNUstep. Mac OS X 10.4 or later required. Mac OS X Universal Binary, including 64-bit support on Mac OS X 10.5. No sub-classing required. Seamlessly adds regular expression support to all NSArray, NSDictionary, NSSet, and NSString Foundation objects with a rich set of Objective-C category additions. Unicode enabled.