Jabba has played about 30k games there in the past few months, human players seem to enjoy playing engines they can beat.
I've been running Jabba in the engine room on Playchess also, but I have the Fritz 13 GUI. It gets hammered by Houdini most of the time with the odd miracle draw.
Don't know if you can get free engine accounts on ICC anymore.
They claim you can get one if you have a human account and you are the original author of the engine.
When I was registered at ICC i tried to get a computer account for running
my gnuchess development branch but the admins did not even bother replying (in fact it seems they never reply to anything, they just take your money). So of course I cancelled my human account as well.
I'm afraid it is correct: you cannot run an engine-engine game without the Fritz GUI, which can be any version as of v8 to the current v13 as far as I understood.
There is little I can do about the need for the GUI, though I can say that authors who do purchase it, do not need to use the Playchess serial it comes with as a part of their engine account. They can use it as a personal player account (to renew or not in the future as they wish), and enjoy the perk of the free Engine Author account separately.
"Tactics are the bricks and sticks that make up a game, but positional play is the architectural blueprint."