It turns out that the person from that Potential Customer That Could Save Us that sent us the cryptic e-mail a few days ago and caused quite a wave of panic was in fact completely mistaken.
He had intended to turn down an entirely different proposal, but instead picked the one that happened to be on top of the stack (ours), used the first email address that he found in it, and sent a completely unparseable message to it.
So we now know that interpreting it as a "No" message was right in way, except that it wasn't directed at us. We also know that apparently it is normal that he would talk with just about as much syntactic correction as Yoda on acids (something which is worsened by french's somewhat more complex grammar).
Hey, I'm not pointing fingers. If I were as famous and rich, I'd probably be stoned or drunk most of the time as well
They're holding a meeting Wednesday, so we ought to know the answer soonish. The suspense still remains, but it already feels better to know that that was a mistake.