CAFE is a test automation ecosystem built around the OpenCAFE framework. The primary components are:

OpenCAFE (https://github.com/stackforge/OpenCafe)
The Common Automation Framework Engine is the core engine/driver used to build an automated testing framework. It is designed to be used as the base engine for building an automated framework for API and non-UI resource testing. It is designed to support functional, integration and reliability testing. The engine is NOT designed to support performance or load testing.

While there is 0 functional overlap with Selenium, OpenCAFE is the architectural equivalent to the Selenium WebDriver. I.E. You would install Selenium WebDriver, and then build automated tests for web browser applications with it. OpenCAFE is the same. You would install OpenCAFE and use it to build API and non-UI resource based automated tests.

It provides many robust features such as over time reliability metrics, multiple layers of parallel execution, clear separation of code responsibilities, a client/behavior/model design pattern that allows for easy serialization, clear support of higher level system behaviors with API clients and much more.

While the OpenCAFE engine is generic and can be used to build a testing framework for any API/non-UI resource based engine it is the core plug-in required for the OpenStack specific CloudCAFE automation framework. This is the primary reason it is hosted along with CloudCAFE/Cloud Roast on StackForge.

CloudCAFE (https://github.com/stackforge/cloudcafe)
CloudCAFE is an implementation of the OpenCAFE core specifically for OpenStack. It is a framework that takes full advantages of the OpenCAFE engine to provide a robust framework for writing complex system level tests cases against OpenStack deployments.

Cloud Roast (https://github.com/stackforge/cloudroast)
Cloud Roast is a plug-in for CloudCAFE. It contains a body of automated test cases for OpenStack. CloudRoast tests support smoke, functional, integration, scenario and reliability based test cases. It is meant to be highly flexible and leave the logic of the testing in the hands of the test case developer while leaving the interactions with OpenStack, various resources and support infrastructure to CloudCAFE.