The software, which Mozilla developer Vladimir Vukicevic characterizes as "pre-alpha" code, is intended for users who want to test the mobile browser and offer feedback.
A Google Groups page has been established for this purpose.
Vukicevic says Fenec has only been tested on Droid and Nexus One phones, but users say they have successfully installed the browser on their HTC Desire and Motorola Milestone phones too.
It's not stable enough for everyday use. Vukicevic cautions that "bugs might cause your phone to stop responding, requiring a reboot."
He also notes that memory use has not been optimized, which could cause problems rendering large Web pages on devices like the Droid which don't come with a lot of memory.
This early version of Fennec also has a habit of quitting and relaunching when it is first started and after the installation of add-ons.
The current build does not allow users to open links to other applications, but Vukicevic expects this issue will be addressed in the next build.
Fennec testers may wish to try an experimental version of Mozilla's Weave data synchronization and sharing API. It's available from the Mozilla Labs Web page.
Mozilla released an alpha version of Fennec for Nokia's Maemo platform in January.
The organization appears to have no plans to develop a version for Apple's iPhone, which requires developers to adhere to certain rules that would limit Fennec's functionality.