As others mentioned, Red Hat (and SUSE) has been amazing for the overall Linux community. They give back far more than what the GPL requires them to. Nearly every one of their paid "enterprise" products has a completely free and open source version.

For example:

  - Red Hat Identity Management -> FreeIPA  (i.e. Active Directory for Linux)
  - Red Hat Satellite -> The Foreman + Katello
  - Ansible ... Ansible.
  - Red Hat OpenShift -> OKD
  - And more I'm not going to list.