As codemastr said in one of the threads I think, the best way would be to point the dns of mircscripts.org to something unaccessible. That way, they will stop. Play hide and seek for a while with them and soon they will be tired of it.
As for threatening, maybe you can threaten to call the FBI or something. It would be helpful if their IP could be traced down and the attacker's ISP found.
And to zack, if we want to stop them, don't DoS them too. They are just little kiddies, if we DoS them, they might think its fun and they will even cause more harm to mircscripts.org.
It seems that the attacks are not as much as before already. I can access mircscripts.org, although thrice as slow as before. I hope fubar will not give up on this website, as it is an essential source for mIRC Scripters.
Be harsh to them, don't be lenient. By all means legal, of course. If it doesn't stop them, track them down.
So sad that these damn kiddies want to stop such a great website...