Unless otherwise noted, the systemd project sources are licensed under the terms and conditions of LGPL-2.1-or-later (GNU Lesser General Public License v2.1 or later).
New sources that cannot be distributed under LGPL-2.1-or-later will no longer be accepted for inclusion in the systemd project to maintain license uniformity.
I can understand critism of systemd for its tools only working with itself and not with any other Unix tools. But it’s absolutely a conspiracy theory to think they’d want to charge for systemd. Though I do agree that if someone was charging for systemd (which they can’t because its open source), open source alternatives would pop up.