io on openbsd - problems installing

Just getting started at looking at io and thought I'd try installing it on my OpenBSD box (Macbook(s) running OpenBSD 4.5 beta).

I downloadeded io-fd8745c00b079963c5bc8398f634cc5651b57bbc.tar.gz...

Untarred etc, gmake'd (make fails, so it looks like a gmake to me)...

Result is

<...lots of compilation stuff...>
cc -MM -MT _build/objs/IoSystem.o -MF _build/objs/IoSystem.d -DINSTALL_PREFIX=\"/usr/local\" -Os -g  -Wstrict-prototypes  
-I. -I./source -I../basekit/_build/headers -I../coroutine/_build/headers -I../garbagecollector/_build/headers  -DBUILDING_
IOVM_DLL  -c source/IoSystem.c -o _build/objs/IoSystem.o
source/IoSystem.c:415:2: #error
gmake[2]: *** [_build/objs/IoSystem.o] Error 1
gmake[2]: Leaving directory `/tmp/io/libs/iovm'
gmake[1]: *** [all] Error 2
gmake[1]: Leaving directory `/tmp/io/libs/iovm'
gmake: *** [vm] Error 2

Anyone encountered this or have advice here?  A quick look at the code suggests a missing conditional compilation for calculating number of CPUs...