Understanding Open Source licenses always turns out to be rather too difficult. At least I always have had issues in understanding which Open Source license is too restrictive and which is a bit liberal.
After looking around for some time, I found the following 3 alternatives for easy understanding of the terms of few of the Open Source licenses.
Marakana have another interesting flowchart for understanding Open Source licenses.
Update: The actual link for the below image is not working anymore.
And finally another option to understand Open Source licenses is tl;drLegal Website, which summarizes and explains Open Source licenses in simple terms and in plain English. Its a pretty decent website which is fast and also very intuitive and easy to use. Just key in the name of the License you want to read about. The website will do the rest with a quick summary and also the full text of this particular license.
I always look up to one of these alternatives when I am in doubt about licensing terms of a particular Open Source License. And when I need to check the complete text of a license, I usually use tl;drLegal Website.