if this is all automated on some kind of script (account creation) then how about changing the name of the register.php link to something different every few hours?
http://eab.abime.net/register.php to
http://eab.abime.net/register1.php for example
Or have a question instead of the Captcha...
For example;
Type in the name of the game at the following (Random) link from the HOL database...