I am not terribly keen on the idea of charging extra to use mods. It's hard enough as it is to get people to sign up for mod games.
What we are considering as a long term solution is to charge a yearly fee, along the lines of the 5 dollars you and others have suggested. The fee would not be mandatory to play however. We would start selling a limited amount of ad space on the website (Not popups. Yeech!) and by paying the 5 dollar yearly fee you would not have to see the ads. Of course this would be "grandfathered" so that anybody that has already made a donation would be paid up already. For those of you that made large donations you would be paid up for several years.
What do you all think about this?
Geoschmo