All Ahren Code software is released under the GPL. You can use these themes and applications without any payment or attribution. If you choose/desire to contribute to these projects, you can do so in multiple ways:

• Code: you can contribute changes to the code if you are into that sort of thing. The sources for all these projects are on GitHub and you should fork them to add your changes and contact me so I can pull your changes in.
• Test: put these tools/themes through the works and let me know if you find bugs. You can create issue reports at Github.

Or, if you are interested, you can donate to one of these organisations: