Basically you need to donate some money, in fact PC really encourages members to donate because every bit of money can help with the forum's server costs. And you get some awesome new stuff with the Supporter title like a green username, profile customization and more. More information can be found here.
Well why don't this community doesn't have their slogan yet??
Well the current PC slogan you see, is actually PC's real slogan. It's just there for fun and probably will never change for the foreseeable future.