So lets get this straight, you released the source code for gPSP and someone has taken that source, changed a bit of bracketing in the code, removed some debug code, added some lines to a config file (most of which were already there) and then released it to the public?
If I were you I'd be withdrawing the source from the next release. If someone is going to modify your source code while you are still working on the project, they should be liasing with you on what changes they have made, and whether it moves the project forward in a suitable direction.
If source code is released, and someone works on that source code and finds a major efficiency gain, that information should be passed back to the original author, so it can be applied to the official development.
The only time a third party should start releasing their own version of a program is when the orignal author has ceased development on the software.
That, of course, is my opinion on the matter. I may be wrong, but if someone at work did that to me on my code that I am still developing, I'd be having a quiet word in their ear. Help and advice yes, underhand changing and releasing of code, no. Maybe its the 10+ years of software development that have given me an undue sense of right and wrong when it comes to source etiquette.