According to the FHS, /usr/local/share/man is the correct man page path in this projects's case. Set this to default in config.mk.
@@ -5,7 +5,7 @@ VERSION = 0
#paths
PREFIX = /usr/local
-MANPREFIX = ${PREFIX}/man
+MANPREFIX = ${PREFIX}/share/man
X11INC = /usr/X11R6/include
X11LIB = /usr/X11R6/lib