Translation from the Russian original, kindly provided by alexsoll:
Custom firmware is being developed and is in final stages of testing at the moment.
14 September 2013 - A new Linux kernel, based on v.126.96.36.199, was compiled for the BlackVue DR550GW
It is significantly different from the original Pittasoft version, namely:
A slimmed down operating system: unnecessary and unused packages, file systems, dependencies, etc were dropped to allow for a faster boot time and a more streamlined operation, with reduced kernel size
Added support for the exFAT file system, based on Samsung implementation of the protocol
Driver for the WiFi RTL8192 card has been updated to the latest supported version: 3.4.4
Added native support for cross-platform networking protocols CIFS (SMB), thus enabling user to mount and distribute directories under CIFS / Samba
Kernel now supports Hisilicon Watchdog & Hisilicon RTC drivers
14 September 2013 - Following numerous tests, alterations and tinkering with the source code, a fully functioning Linux kernel for the DR550GW was finally compiled and loaded onto a test camera. It worked! This basically means that we now have a fully-fledged Linux operating system, with all the flexibility to add and adjust certain functions and options, that comes with it.
In the works:
Implement native support for exFAT file system at the kernel level (so that any SDXC-compliant card will work)
Audible Speedcam warning system
Despite the fact that WDR was not available as a factory option, it will be implemented in the custom firmware, along with a number of other options, in the forthcoming firmware updates