GIMP is Free Software and a part of the GNU Project. In the free software world, there is generally no distinction between users and developers. As in a friendly neighbourhood, everybody pitches in to help their neighbors. Please consider the time you give in assistance to others as payment.
Ways in which you can help:
As you can see, anyone can help.
The team is currently busy working on v2.10. This will be the first release of GIMP featuring a new, advanced image processing engine, high bit depth editing, as well as new and improved transformation and selection tools.
Porting internals of GIMP to GEGL is mostly done, but more plugins have to be ported to GEGL, and GEGL needs to be made faster. If you are willing to help with that, please refer to the Porting filters to GEGL page to see what you could work on.
To get a better understanding of where the project is heading to, which features are planned etc., please visit the Roadmap page.
GIMP is not a bug-free application nor is any other application so reporting the bugs that you will encounter is very important to the development, it helps the developers to make GIMP more stable and more bug free.
You don’t have to be a developer or a everyday user to report bugs. It can be hard to report a bug the first time you try it out but don’t just quit the whole bug report if you think it is hard. Instead, look at the bugs page you will find some very good help about this.
Creating websites that contain useful information is very important. It is actually just as important as doing bug reports. A website contains a lot of information that is needed for the development to move on and it also contains information that will help the public to understand what the application is all about.
gimp- the GIMP application itself
gimp-web- repo for this website
gimp-web-devel- repo for the developer site at http://developer.gnome.org
gimp-help-2- the GIMP user manual
New contributors should first introduce themselves on IRC (the #gimp channel at irc.gimp.org) and/or the relevant mailing lists:
This way you can announce the changes you intend to make, ask questions, and discuss which changes would be best. It’s generally better to focus on one thing at a time. Contributing to a software project for the first time is always the hardest part, which is why we’re here to help each other. There are also websites to give you a good look at how hacking is being done in GIMP.
The site you should keep updated with and the site that is updated all the time with new development help guides is located at http://wiki.gimp.org/. If you have GIMP installed at the moment then there are some files you should look at in the source code that might help you a little.
Once you’ve figured out what to do, though, be bold and get to work!
The GIMP community is a friendly one, but it probably is still worth saying this: Try not to take critiques personally. We all just want GIMP to be the best that it can be. Once approved, your edits will be merged into the code base, making you an official GIMP contributor. And if you keep up the good work, not only will this process get easier with practice, your administrative privileges in GIMP development will also increase too.
The main GIMP development website
An image processing library based on GObjects
babl A dynamic, any to any, pixel format translation library
GNOME GIT source code repository
The Unstable GIMP page lists the lastest source code commits to the unstable branch of GIMP.