About a year ago, JetBrains started a licensing program for Open Source projects. In short, developers of active and vital Open Source projects can request and get free IntelliJ IDEA licenses.
Today more than 300 Open Source projects received these licences. Among these projects there are a lot of Apache participants including members of Ant project, Geronimo, Tomcat, Tapestry, Maven and Struts projects. Other open-source projects receiving licenses include BeanShell, CruiseControl, JBoss Portal and AOP Aspect Libraries, JPublish, Jython, Open Symphony, and Spring Framework.
Almost everyday a new project enters this program. One of the participants, Glazed Lists, has published a set of screencasts that show how to use Glazed Lists API. Guess which IDE was used? Right, IntelliJ IDEA. Although the screencasts use only about 10% of IntelliJ IDEA features, they are impressive enough to make new Open Source projects enter this program.
So, if you are one of the Open Source developers, join now and develop with pleasure!