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Core UI widgets: The amount of different widgets in the core product, and how rich in user interaction those widgets are. One star is for basic (X)HTML widgets, two stars signify basic interactivity and noticeable richness in widgets. Three stars mean a good selection of fully rich widgets.
Page request/application oriented: Whether the resulting software looks and feels like a traditional webpage, where most or all interactions result in a full page refresh, or if the resulting software looks like a desktop application where only small parts of the browser window is updated at any one time.
Portlet support: Vendor makes an explicit effort in making sure that the Portlet specifications are met and fully supported by the framework itself.
Documentation: The availability and quality of framework documentation. One star signify basic documentation, like API documentation. Two stars can mean available commercial books or a few and/or simple online-tutorials. Three stars mean a free book or extensive examples and walkthroughs/tutorials available.
IDE support: How well an IDE supports working with a certain framework. One star means the overall possibility of developing with the framework. Usually this means supporting the underlying language. Two stars stand for a plug-in that helps you with some of the basic things like setting up a project or configuring some of the settings for you. Three stars means a fully-fledged plug-in with advanced specialized features like WYSIWYG editing.
Simple workflow with plain text editor: This mark is earned if the framework is easy and simple to work with without any kind of IDE support. Usually this means no need for constant recompilation and redeployment, which is often done manually or in the background with IDEs.
Specialized UI widgets for mobile: Does the framework provide widgets specially designed for touch-controlled mobile user interfaces, like mobile phones and tablets.
Also remember to check out RebelLab's "The 2014 Decision Maker's Guide to Java Web Frameworks"