It is asking for Licence key each time I open the calipers. Can I avoid this?

FYI - I am normal user don't have admin rights, not an admin user.

Please notice the following suggestions:
1. First please login using an Administrator account and try registering the applications
2. If that doesn't work, then while still being logged in using the Administrator account, right click the application (Screen Calipers, etc) and select the "Run as Administrator" option and then try registering the application the way you normally do.
3. Finally please take a look at the following forum post for a solution:
http://www.iconico.com/discussions/view.aspx?id=127&forum=1

Usually, point 1 solves the issue.