It should stay greyed out, simply because the original developer no longer supports it and hasn't updated the version info - but from the comments on the page the basic functionality seems to have transferred nicely and so fiddling with the compatibility info inside the .xpi file is all that is needed to make it work.

I just hope it works as advertised ^^ on Firefox 7 - the hacked version definitely works on my Firefox 3.x - the hacker did say he set the version limit to 9 so if it works you should be able to use it until then.

I usually use AdBlockPlus and never see any of the advertisments on Mediafire and it works no problem. Still, I have heard NoScript is supposed to be very useful as well.

Go on soothe your soul!