Open source ISMS
SecBoard Community Edition publishes the ISMS/GRC source under AGPL v3. You run it on your own Linux host. The community key covers up to 100 users and does not expire as a subscription.
What the community edition includes
The pricing page describes Community Edition as the full ISMS/GRC source, not a feature-cut demo. The installation guide says that source is Python, without Cython or Nuitka, and that the community key allows up to 100 users. Enterprise is the other half of the dual license: a commercial key when you need more users, closed modifications, enterprise modules, or an SLA.
What you can read before installing
The public repository is on GitHub. The manual covers installation, system requirements, the first administrator login, and the demo is on demo.secboard.online. AGPL v3 applies to the community source: if you distribute a modified version, the license obligations travel with it.