This is fantastic. AFAIK there are no Lisps our there that are designed with games in mind which is a huge shame because I often think how perfect it'd be for game dev (Arcadia and Nightmod spring to mind but imo they're shoehorns. Good ones, but still).
There are a couple of high-performance, low-latency lisps, either with a low-latency GC or refcounted or compiling to C as Carp does.
ECL (also typed), Vicare, Larceny, Ypsilon, the new guile, Gambit-C, Chicken, Chez, Bigloo, stalin, Corman CL, or fast typed CL: sbcl, franz, lispworks and few more.
Or the ones compiling to LLVM or JVM or .NET. Most prominent Clojure with a very unlispy syntax.
And note that you simply get a low-latency GC with libgc (Boehm-Weiser) by using the incremental GC with GC_enable_incremental() and SMP with parallel marking phases -DPARALLEL_MARK. http://www.hboehm.info/gc/scale.html
This is no voodoo nobody ever managed to do, even if most blog posts for popular not-invented-here languages state the opposite.
Of course libgc is pretty simple and slow, good for foreign code (i.e. ffi's needed in games), slower than Cheney-2 finger copying allocators which I got down to 10ms, compared to 100-300ms for mark-sweep. But copying collectors need 2x memory, so not usable for small devices such as phones.
And a bit complicated for foreign memory, which prefers conservative mark & sweep.
