I checked that thread. This campaign is NOT a PPP (pay per post) campaign.
We are asking participate to at least make a post in our own ANN and bounty thread, so that we can make sure that the person who join the campaign are using our avatar and signature as requested. This enables us to award the people who do the work and contribute to this project, and filter out the ones that don't.
I could be mistaken, but I'm under the impression that whether the campaign is paying per post or full term is not relevant. Also, you don't really need users to post in those specific threads just so you can make sure they are using the campaign signature and / or avatar (although I understand the desire to have them participate in your threads / projects).
Still, I would check with the mods if I were you, just to make sure they have no issues with it.