Two years after the Oracle ADF Pricing post we have good news regarding the licenses for the  ADF libraries.

Oracle ADF Essentials

Faster and Simpler Java-based Application Development – Now Free

Oracle ADF Essentials is an end-to-end Java EE framework that simplifies application development by providing out-of-the-box infrastructure services and a visual and declarative development experience. Oracle ADF Essentials is free to develop and deploy.