Now the BLHeli firmware/software suite is available also for Atmel ESCs.
The ESC firmware source code is published here: https://github.com/bitdump/BLHeli
The BLHeliSuite PC software can be found here: http://www.helifreak.com/blog.php?b=2162

The Atmel version of the ESC firmware is a direct conversion of the current Rev11.2 SiLabs version.