legally you are not allowed to redistribute it, read apple's EULA in itunes. then again you're not allowed to jailbreak either..
word of advice from a long-time jailbreaker. do
not i repeat do
NOT upgrade your OS to 4.0, 3.1.4, 3.2, or whatever new version is released if you want to keep your jailbreak. if you're one of those people who has to upgrade
immediately you may find yourself locked out and unable to jailbreak at all if the team is not able to find a new method to break into the OS (which is getting harder and harder with each release, apple closes up security holes the dev team exploits). also do not post and bug the dev-team asking when a new jailbreak will be released, it will be released when they have verified it works and is safe. it may take
weeks (and i mean 2-3 months) after 4.0 is released before a jailbreak is let loose to the public, as was the case when 3.x was released.
if you're going to jailbreak it pays to educate yourself a little by following the
dev-team blog on their web site or on
twitter to prevent future issues.
i also strongly recommend reading the cydia FAQ and saving a shsh for your iDevice to help insure you can jailbreak in the future.