The rpm-ostree-libs package includes the shared library for rpm-ostree.
acquired package info from repodata DB: repodata/f1f85c23079e7764ad00378a9fc5d660b89a03657290e75426caf7be5b7da462-primary.sqlite.bz2
The rpm-ostree-devel package includes the header files for rpm-ostree-libs.
The ostree-devel package includes the header files for the ostree library.