I think they said in the primedice thread that it would be open to everyone and that they had 50 bitcoins for the campaign. They even showed what the rate will be for each section of the forum.
But I don't know how much longer they will take before opening up lol. xD
The rates were given as an example only. They will be different. PD is currently only open to Staff but with the re-launch it will be opened up to other Membergroups but likely not all of them. At least the few higher ranks.