OpenNMS is delivered as two different, completely open source, distributions: Meridian and Horizon. Both distributions are built from the same open-source code base; however, the release cycle and the support options available vary for each.


  • Following the “release early, release often” model, OpenNMS Horizon contains all of the newest features developed for the platform.

  • Horizon is freely available to download and contains the newest features that are updated on a rapid release schedule.

  • The OpenNMS community drives the development of Horizon along with The OpenNMS Group, one of the largest upstream contributors.

  • Community members may contribute via Pull Requests against the GitHub repository.

  • Horizon is licensed under the Affero General Public License (AGPLv3).


  • OpenNMS Meridian is a subscription service that provides access to an optimized and very stable version of OpenNMS that maximizes the platform’s value and minimizes the effort required to maintain it.

  • Features that have proven to be stable and effective in Horizon will eventually be merged into Meridian.

  • Meridian is licensed under the AGPLv3, the same license as Horizon. Purchasing a subscription to Meridian will provide access to the Meridian binaries accompanied by the Meridian code.

  • For organizations that have a policy against using software published under the AGPL, Meridian is also available under an optional proprietary license.

  • Meridian is initially offered via RPMs Red Hat Enterprise Linux and CentOS.

Which distribution is right for you?




Monitoring of new technologies and IT ecosystems such as Docker, SDN/NFV, and virtual systems. Enterprises and businesses looking for stable platforms with long term support

Development Model

Open Source Open Source


AGPLv3 AGPLv3 or optional Proprietary License

Release Cycle

3-4 months 12 months


Community supported mailing lists and wiki, OpenNMS ULTRA support product Several options available, access to the OpenNMS Connect forums

Feature Selection

Exploration of new technologies to test value to drive rapid advances in management technology Features chosen for level of stability, usefulness and quality of integration with existing code


User and community configured and maintained Preconfigured events, notices, data collection, workflows and reports


Community driven Access to update server for latest bug fixes and performance enhancements


Free download Yearly subscription per management server.


After new features are proven to be stable and useful in Horizon, they get integrated into the upcoming release of Meridian.  Releases are managed through JIRA, a publicly available issue tracking software.

Horizon Release Workflow

  1. Development: New features are developed and changes in architecture and major bug fixes are implemented. To install this version, download the OpenNMS Horizon SNAPSHOT release. Changes are merged from pull requests after reviewing and testing them. Major releases can require configuration changes or data migration.
  2. Feature Freeze: No features are pulled in develop branch. The code base gets stabilized and is prepared for a first release candidate.
  3. Stabilize code: Problems are solved, missing unit tests are added, outstanding reviews are done, fixes are made, and focus is on getting Continuous Integration green. The code is prepared for Release Candidate 1.
  4. Release Candidate 1 (RC1): RC1 is the test phase driven by OpenNMS community. Hotfixes can be made and applied to development branch during the test phase.
  5. Release Candidate 2 (RC2): Test phase with applied hot fixes from RC1
  6. Release: This is the date of a new OpenNMS Horizon release, which can be installed as a stable release.