a new platformer being put together by Might and Delight, and when it arrives, it'll be available on PSN, Steam, and XBLA. But while Might and Delight will be self-publishing on PSN and Steam (because both platforms have plans in place for devs to do that), it won't be self-publishing on the Xbox Live Arcade. They won't have another publisher, either -- instead, Might and Delight is "renting" an XBLA game slot.
The PA Report explains how it all works: When Microsoft agrees to allow devs to publish on XBLA, those devs get a set number of slots to sell games with. Not all of the publishers who get these slots use them and some of those publishers are now selling their slots, usually for a share of the game's profits, to other developers. That's the case with Pid: Might and Delight is "borrowing" another publisher's game slot and in return sharing part of Pid's profits.
Anyone publishing a game on XBLA needs to give Microsoft a cut of the profits as well, so both Microsoft and the publisher are taking money away from Might and Delight here. But on the plus side, Might and Delight doesn't need to make a traditional publishing deal at all, so there's no issue with exclusivity or long-term rights. If the game does well, they're much more likely to make sure they see the rewards directly.