I am aware that Linux is a Unix-like operating system and also it does not use any source code of Unix..I came to know that in early stages unix had sued linux for having stolen significant part of Unix's code...
Are you aware that this is incorrect??...
there are a whole bunch of Gnu utilities that can be used on any "Unix-like" system, including Linux, BSD, etc.
Unix is not one specific system---there are many flavors--some of which have now become "open".
Unix is not a legal entity and cannot sue anyone---especially not Linux (which is also not a legal entity) Perhaps you were referring to SCO suing IBM?
I am having a doubt related to the following:
When root user or normal user changes his password the system asks for "UNIX password...". Why it is like this...? why it is not asking for linux password .
Is n't that a violation....?
Violation of what??
the utility giving you that message---from Gnu or otherwise---has its roots in the Unix culture and methods.