What ist the difference between iText-2.1.7.jar and iText-2.1.7.js2.jar?

What is the difference between  iText-2.1.7.jar (found in jasperreport 4.5.1) and  iText-2.1.7.js2.jar (found in jasperreport 5.0.4.) concerning

• license
• source-code changes (we use iText-2.1.7.jar for both jasperreport and direct use)

Thank you