Who are cGmail developers?

Well, there is only one developer for now. I'm Marco Ferragina an italian open source entusiast.

There is a development repository?

cGmail is now hosted on launchpad and use bazaar revision control. Here you can find the repository

My language is not supported! What can I do?

Why don't translate by yourself and send me the translation? I will include it in next version.

How to set the default browser and default mail reader used by cGmail?

cGmail will use gnome default browser and mail reader. So if you want to use a different one you must change it from gnome preferred apps.