Oso is described as 'Engineering teams use Oso when they’re done rolling their own permissions. It lets your application answer questions like “can this user read that document?” and “which objects can this agent manage?”' and is an app. There are four alternatives to Oso for a variety of platforms, including Self-Hosted, Python, .NET Framework, SaaS and Cloudron apps. The best Oso alternative is Keycloak, which is both free and Open Source. Other great apps like Oso are Aserto, Permit.io and Cerbos.