I have one doubt. I would like to develop one web application using GWT. I use the jars which are provided by the GWT in my application. Now, can I sell my application for commercial purpose? In other words, can GWT jars used for commercial purpose for free of cost?
If you're planning to use GWT for "commercial purposes" then asking strangers for legal advice about that is not a good commercial strategy. You'll want proper legal advice in that case. I'm not surprised you don't understand how that licence applies to your situation, if I were running a company I probably wouldn't understand it accurately either.
Joined: Mar 22, 2005
For a summary of the Apache license you can start at its Wikipedia page. But as Paul said, you need proper legal advice that's tailored to your situation.
You can distribute the jars provided
1) You do not make changes to the source code
2) If you do, you need to provide the source code
3) Your distribution must have the license file
4) You must tell the users where the license file is
Disclaimer: I am not qualified to provide legal opinions. Like Paul said, consult a lawyer.