I don't know for sure, but it all depends on your ad placements. My suggestion would be to copy DPs ad placement and put them on your forum I guess that the owner of DP knows where to place them.
If you mean CTR, that's worst due to some of forum member are old mebmer who wouldn't click anymore. if you mean the best forum palcement, below image for forum
yeah its all about ad placement , ads that get in-you-eye , ive seen it on a few forums where they have the first post as an ad itself so does catch the eye.
The best ad placement for vbulletin forums is first in the threads list. You insert a half-banner ad right into the threads list. I'm getting about 5% click-through (got a couple complains from members though). The second best spot is right in the post at the end of all text. Where ever you place the ads, don't put it on top in the header like DP does. DP earns mainly through CPM ads. DP's eCPM is extremely low, and that you should not follow its model/placement at all. I know many other secrets that could easily achieve $10 or $20 eCPM easily on forums. It's just you have to guts to do it or not. Adsense is ok with it, because I do it for more than 12 months just fine. My methods are just optimizations, so little harm done.
make sure your niche is specific or else Vbulletin ads or forum ads will appear..and they have a terrible cpc.