It's possible people will be getting rebate "gift cards" that can only be spent in certain industries, like retail and stuff. So, whether you can donate it to Ron Paul or not is up in the air.
It is difficult to coordinate these things. We tried. We ran three or four threads in this forum and posted the announcement on Grassroots Fundraising Projects forum.
However, not everyone is browsing all of these forums all the time, so things get missed. It's just the way it is.
It doesn't really matter though. Sign up at one site or the other. Both sites will coordinate on the donation date. We're all on the same team, after all.