vpopmail currently has RESTRICT=nouserpriv because the configure script fails if it is not run with uid 0. I have no idea why that check is there, but I confirmed that removing the "RESTRICT=nofetch" line from the ebuild and adding the following line to src_unpack() sed -i -e 's/\(`$idcommand`\)/false && \1/' configure.in configure produces identical results.
fixed in 5.4.19