Put in several GNU-bot's and see if the participation drops.
Yes, I can imagine that participation would drop: not for fear of
loosing one rank but because it would be a BORING tournament.
But you keep going back to that tired argument while nobody ever said
that clones should be allowed. (Other arguments like comparing the
effort involved, the investment needed for the hardware, "fairness", I
find silly.)
Again: SlugGo is not a clone GNU Go. The problem is the broad ban of
"derivatives" which covers a large scale of situations. (And BTW, as
far as we know, GNU GO code could be included in unknown numbers of
closed programs to help them win against GNU Go. Cheating is dealt for
by the honor system, quite good, but programs rightfully and openly
based on GNU Go should be banned?)
Banning GNU Go-based metamachines really looks like trying to avoid
potentially strong new comers. This is not a good way to advance the
state of the art.
But of course, this is still the organizers call, and anybody
disagreeing could always set up another environment, with rules more
open than that of the "1st division", but less than the "open" where
armies of clones could, I agree, make for a boring circus.