Originally posted by plenderj
What I meant was that if they want to grab of the screen on the mainframe, they could write an app to do it.

And if the system happened to be running a popular *nix operating system, then there may already be an easy way to do it, through the use of 3rd party applications
What you are referring to as "want to grab of the screen on the mainframe" is also called a Screen Scraping and there is no way (easy or not) without third party's interface (whatever that may be: OCX/API)