Looks like you forgot to add it to your PLIST file.
Code:
--- PLIST.orig Mon Sep 7 06:50:07 2009
+++ PLIST Mon Sep 7 06:51:06 2009
@@ -1,2 +1,3 @@
@comment $OpenBSD$
@bin bin/gambatte_sdl
+@man man/man6/gambatte_sdl.6
Perhaps you should check and see if anything else should be installed besides the program executable and a single man page..
Good luck, porting is fun eh?