shibajisanyal,
gnu.getopt.Getopt.<init>(Getopt.java:617)
Getopt.java
...
617 if (System.getProperty("gnu.posixly_correct", null) == null)
618 posixly_correct = false;
619 else
Your code is trying to access system property thus java security is blocking it
Atleast if you could sign your applet, Java will ask you if you trust the applet or not ..
.. Following links might help you ..
Chapter 10: Signed Applets
keytool-Key and Certificate Management Tool