That gas connection looks homebrew also. I think it's just a regular portable gas grill hooked up to a regulator at the tank. You MUST have a regulator somewhere in the line.
The mount is just a brilliant idea but homebrew for sure. I like the fact that when pulled out it seems to be far enough away from the trailer to not melt anything.
Not sure what keeps everything from rattling itself to death though when on the road.
The slide tubes run al the way across the 5 whl bed, plus there is a catch to keep it from sliding out. Last touch, there is a screw mounted in the lid that pushes against the frame rail when retracted.
If it is a home brew mounting rack, it is well made and finished.
The grill itself is off the shelf as is the LP line which is Td into the regular LP lines to the trailer.