Our themes are GPL and free to download. This gives anyone out there the opportunity to send us bugs and/or bug fixes and contribute code. In fact, we have had several of our PRO members contribute back useful customizations in the support forums. I think making our themes available as a free download encourages participation from other developers.

Right now we are in the midst of internationalizing our most popular theme, Vigilance, so we are looking for international users to help with that process.

Of course, spreading the word to your friends and colleagues is oftentimes the best gift you can give back to a theme developer.