as far as I know if you create a gravatar account and are using gravatar for avatars in mojoportal, then as long as your account on the mojoportal site is using the same email address as your account on gravatar then it should show your gravatar avatar.
your gravatar is showing here on this site in your forum posts so you appear to have a gravatar and it is working here. as long as your email address is the same in your own site it should work there just as it does here.