Looks like Geohot has made more progress with respect to fully understanding and hacking the PS3’s innards… Check it out:
SourceAs some people in the comments called, it's an RCO file edit, just like RCO edits on the PSP(almost same format too).
RCO files are resource files for VSH plugins, live in the dev_flash, and aren't signed.
To edit them on your system, patch your hypervisor to allow encrypted access to the partition(flash on old systems, hd on new), and
mod ps3pf_storage. dev_flash is just a FAT partition, mount it in Linux and change what you'd like.