It sounds like what you have is a patch you would like to submit to the author. Have you contacted him? Unfortunately his software doesn't (appear to) include a license so it may be hard to proceed from a legal standpoint. Most of the time in the open source world, if you encounter a non-responsive (or unwilling) author, you can do as you have already done, fork and patch. At that point you can choose to publish your new version, possibly with a new name, and conforming to the author's license.
From a software standpoint, the code is rather ancient, written for Perl 4. Because Perl has excellent backwards compatibility it will probably still work, but the question is, do you really want to? It may depend on your use-case. The original author was making gifs to use in web pages. If this is what you are doing, you might want to look at MathJaX which lets you use LaTeX right in your browser/HTML directly.