I think it may be a great addition to have the featured ones on the home page limit itself to one that was active in the X amount of times. So the most active forums in the last 7 days would get more hits, etc.

This would be great for browsing the directory, activity in the last 7 days should get higher ranking priority.

By activity I mean posts & threads CREATED within the last 7ish days.

I don't think thats a good idea at all. The reason for that is it allows the sites that are less active to have more of a chances to draw in hits as the sites are generated at complete random. Doing as you suggested would become favoratizm in time.

I quite like the idea in fairness.
The problem is, currently the directory could throw up 20 inactive boards, compared to say 20 active boards.
Means you might also discover some forums which are actually really active on here, but have never heard of because you dont see them about support.

A great majority of the boards I keep seeing featured had their last post 6+ months ago it seems. Would they come back alive with no other members? Only one person alone?