This is not an attempt to comprehensively list all users of these APIs. We are just listing the most obvious/prominent ones which come to our mind.
Of course, one last thing I can't make myself not ask you before we finish here, and before you start reimplementing these APIs in your distribution: are you sure it's time well spent if you work on reimplementing all this code instead of just spending it on adopting systemd on your distro as well?
+
+## Independent operation of systemd programs
+
+Some programs in the systemd suite are indended to operate independently of the
+running init process (or even without an init process, for example when
+creating system installation chroots). They can be safely called on systems with
+a different init process or for example in package installation scriptlets.
+
+The following programs currently and in the future will support operation
+without communicating with the `systemd` process:
+`systemd-escape`,
+`systemd-id128`,
+`systemd-path`,
+`systemd-tmpfiles`,
+`systemd-sysctl`,
+`systemd-sysusers`.
+
+Many other programs support operation without the system manager except when
+the specific functionality requires such communication. For example
+`journalctl` operates almost independently, but will query the boot id when
+`--boot` option is used. `systemd-journal-remote`, `systemd-journal-upload`,
+`systemd-journal-gatewayd`, `coredumpctl`, `busctl`, `systemctl --root` also
+fall into this category.