According to Mike Westerhof it is obsolete and can be removed:
http://patchwork.openembedded.org/patch/922/
+++ /dev/null
-DESCRIPTION = "RPC program number mapper."
-SECTION = "console/network"
-LICENSE = "GPL"
-PR = "r2"
-COMPATIBLE_MACHINE = "nslu2"
-
-SRC_URI = "${DEBIAN_MIRROR}/main/p/portmap/portmap_5.orig.tar.gz \
- ${DEBIAN_MIRROR}/main/p/portmap/portmap_${PV}.diff.gz;patch=1 \
- file://no-libwrap.patch;patch=1;pnum=0 \
- file://portmap.init \
- file://make.patch;patch=1"
-S = "${WORKDIR}/portmap_5beta"
-
-sbindir = "/sbin"
-
-do_compile() {
- oe_runmake
-}
-
-do_install() {
- oe_runmake 'docdir=${datadir}/doc/portmap' 'DESTDIR=${D}' install
-}