I've had one of these for a few years as well... some notes I've taken:
Motherboard is a custom short run (BARRACUDA) from Intel based on the D915GAGL platform.
Board options included are Gigabit Lan, iee1394, and TPM.
TPM is pre-programmed with the keys required to decode Finder and other Apple encrypted binaries.
BIOS is an early reference bios, but with Apple quiet boot splash screen.
The case is a modified PowerMac A1177 without the partition in the air deflector.
The Power Supply is the official G5 power supply, but with an interposer to convert to ATX+4 power.
The Motherboard is extended past the MATX form factor to meet with the Apple ports on the G5 case.
It is mounted on a frame that then attaches to the G5 board mounts, as G5's are not ATX compliant.
There is a populated (but cable not provided) header for VGA on the back of the board.
Video out is DVI-D only by way of a standard ADD2-N card, but while retail ADD2 cards are identical, those with VGA options do NOT work.
Presumably connecting the VGA header will yield via video using the onboard chipset, and the collision of the external VGA on an ADD2 and the onboard prevents the system from booting properly.
Unsurprisingly, dumping the DTK bios and installing it to a RETAIL D915GEV/D915GUX/D915GAV/D915GAG will work perfectly, and if you apply the decryption patch to the marker disc, no additional means are required to install and use it just as you would a real DTK.
Because the system is BIOS based (and a P4), there are very few upgrade paths (beyond 10.4.3 8F1111) for the system if you plan to run OS X without a full fledged chameleon or similar install.
other _OLD_ photos of mine while i was fixing some issues from a poor shipping job:
https://www.flickr.com/photos/defor/sets/72157624223360933