Understanding what Cloud Foundry is all about : CHOICE
Being an Open Platform as a Service is about having the ability to make the choices that best fit you as a developer:
Choice of Developer Frameworks (The Top of the Triangle)
Today (In the initial release) Cloud Foundry Supports Spring for Java, Rails and Sinatra for Ruby, and Node.js. There is also support for Grails on Groovy and other JVM-based frameworks baked into Cloud Foundry. It is important to realize that this is only the beginning; there will be support for other frameworks (and languages) as Cloud Foundry matures.
Choice of Application Services (The Left Side of the Triangle)
Application Services allow Developers to take advantage of data, messaging, and web services as building blocks for their applications.