Well, he did post some source code, which was quite the mess as a lotof reader macros were used, but it was still readable CL, so I'd opt for 2, except that some of the pseudocode he posted was pretty strange, meaning 1 wouldn't surprise me either.
Other options that I can see: 3. trolling, trying to make it seem like Lispers wouldn't post the code they write (I always do if I'm discussing my code with someone else; if it's something I wrote for myself or not for public consunption, I just don't talk or publish it) 4. He wants to use it in some commercial software he wrote or doesn't want to reveal his identity (unlikely for a variety of reasons)