Ok, here's the story, as unbelievable as it sounds. It looks like the message was a call for help, sent by the ship that also appears in the sequence of pictures. The ship seems to be called Arrow and to be a sentient being, or at least intelligent. Apparently the story as told by the picture sequence has actually happened, with the final picture (decrypted by us today as expected) happening three months ago, about when the message was sent to us.
It is the story of Endo, a specimen of the extraterrestial Fuun. Endo was garbage-collected while sleeping in his(?) ship Arrow and unfortunately drifting into a heap of junk. Garbage collectors are apparently common in space and run by a species called the Imps. They like to drop junk on underdeveloped worlds (sorry, this is what Arrow told us). So the ship, together with lots of other stuff, was dropped on Earth. Arrow was damaged in the process, and before it could warn Endo that the atmospheric conditions of Earth are not very suitable for a Fuun, Endo left the ship – only to be hit by a cargo container! Endo is now in serious trouble. According to Arrow, the only chance to save Endo is to adapt him to the conditions that are prevalent on Earth by changing its DNA.
The hitch is that Arrow, being damaged itself, is running low on energy and cannot come up with a good modification itself. It can still perform the actual transformation process, but only if it gains knowledge of a suitable transformation soon. Arrow tells us it only has slightly more than 72 hours left before it will shut down!
During the last days, we have been able to decipher large parts of the original message, found out that it is about DNA and describes how Fuun DNA works. We therefore have some understanding now about the process involved. Unfortunately – and we feel really guilty about it – we have given all of this a low priority due to the upcoming contest, and the one thing we didn't find out until after we actually made contact with Arrow, was that this really is a cry for help, and how urgent it is! If only we had found out earlier, we would have had much more time to save Endo!
Because of that, and also because it is really the only thing we can think of to still give Endo a chance, we will change our plans. We will abandon the original topic we had in mind for the ICFP contest (writing generic programs in order to design boilerplates). Instead, we make it the task of the contest to Morph Endo!
(Of course, we still are not 100% sure if the message is actually authentic, but from what we've seen, there seems to be a lot of structure in the DNA we discovered, and a lot of information provided by Arrow, and we doubt someone would put so much effort into a joke.)