From: [email protected]
Subject: http://www.jetbrains.com/idea/opensource/asf.html

To request your free IntelliJ IDEA license, simply send an e-mail request
from your e-mail account at apache.org to Ilya Dumov
[email protected].

You'll receive a reply at your apache.org address with a link to a web
page where you can confirm your details. After your confirmation, you'll
receive your license key by e-mail within 2 business days.

That's it! We look forward to your participation in our Open Source
initiative and thank you for your interest in IntelliJ IDEA.