Warning: Be aware this PS3 CFW is still under development, and like all PlayStation 3 Custom Firmware should only be installed if you are aware of the risk of possibly bricking your console. Although not a requirement, ideally it should only be attempted if you have a backup of your PS3 NAND / NOR and a hardware flasher available.
To quote, roughly translated: Hi all, What better than to come back with this kind of news!
Our friend and SGK developer releases today the result of hard work. Indeed, in the shadow he worked to bring us a CFW with features interesting and not yet seen the new CFW 4.xx
The basis of this CFW is based on the REX Rebug CFW 4.21 which is the most stable and most successful of the moment. He added the Debug menu and Rebug Package Manager for our greatest pleasure.
Some files from firmware 4.30 which ensures compatibility for the latest keysets. So you can play your backups favorites without a patch or fix. 4.31 is a spoof includes access to PSN and avoid unintended updates.