All the extensions on this site are released under GNU General Public License Version 2. I can be contacted through the contact form on this site and you will also find me on IRC at #joomla@freenode.
If you would like to contribute to any extensions, you will find the github repository at https://github.com/rvsjoen/joomla-extensions
If you happen to find any bugs, those nasty little critters can be reported at the following url:
Just label the bug with the correct label for the particular extension.