osm2pgsql dropped the dependency of geos. The only proof i could find by quick search is in this issue: https://github.com/openstreetmap/osm2pgsql/issues/700
And here is the accepted pull request discussion: https://github.com/openstreetmap/osm2pgsql/pull/684
commit 0782b03149241c4f94006e90c56e06170e2e2256 Author: Aaron W. Swenson <titanofold@gentoo.org> Date: Sun Apr 23 09:48:24 2017 -0400 sci-geosciences/osm2pgsql: Drop sci-libs/geos dependency No longer depends on GEOS. Bugs: 616270 Package-Manager: Portage-2.3.3, Repoman-2.3.1