1. Auth0's Authentication Capabilities: Auth0 is primarily focused on providing authentication and authorization services. It offers various authentication methods such as social media logins, multifactor authentication, and passwordless authentication. Auth0 also supports user management, user roles, and permissions to control access to resources. In contrast, oso is a general-purpose policy engine that can handle authorization logic, but it does not provide out-of-the-box authentication features like Auth0.

2. oso's Flexible Authorization Logic: oso enables fine-grained control over authorization logic within an application. It allows developers to write policies that describe the rules for granting or denying access to specific resources based on various conditions. These policies can be easily modified without changing the application's code, providing flexibility and adaptability. Auth0, on the other hand, relies on predefined authentication and authorization workflows that are less customizable.

3. Integration with Different Programming Languages: Auth0 offers libraries and SDKs that seamlessly integrate with a wide range of programming languages and frameworks. This allows developers to easily implement authentication and authorization features in their applications regardless of the technology stack used. oso also provides bindings for multiple programming languages, enabling developers to enforce authorization policies in different environments.

4. Support for Access Control Lists (ACLs): Auth0 supports the use of Access Control Lists (ACLs) for managing permissions and access control. These ACLs can be used to define fine-grained access rules for specific resources, such as files or database records. oso, on the other hand, focuses on policy-based authorization, allowing developers to define more complex and dynamic authorization logic beyond simple role-based access control.

5. Ease of Integration with Existing Systems: Auth0 provides prebuilt integrations with various identity providers, such as Google, Facebook, and Microsoft, making it easier to integrate external authentication services into an application. Auth0 also offers Single Sign-On (SSO) capabilities, allowing users to authenticate once and access multiple applications seamlessly. oso, on the other hand, is not an authentication provider and requires integration with an existing authentication system or service.

6. Testing and Auditing Capabilities: Both Auth0 and oso offer testing and auditing capabilities, but in different contexts. Auth0 provides testing tools for validating authentication and access control workflows during development and deployment. It also provides audit logs and reporting features to track user activity and troubleshoot any issues. oso, on the other hand, provides tools for testing authorization policies and ensuring they accurately enforce the desired access control rules within an application.

In Summary, Auth0 is primarily focused on authentication and offers a wide range of convenient authentication features and integrations, while oso is a flexible policy engine specifically designed for authorization logic and fine-grained access control rules.