Helper variable that controls progress off the predefined LicenseDlg dialog box: if nonzero, the Next button in that dialog box is enabled and the user can continue to the next page; if zero, the button is disabled. The variable is linked to the I agree... check box on the same dialog and is set and reset by that control.
You can refer to this variable as <UILicenseAgreed>. In conditional expressions you can omit the brackets and use tests like UILicenseAgreed. By default this variable is set to 0, so the user must check the I agree... check box on the predefined LicenseDlg dialog box before continuing. However, you can set this variable to 1 to pre-check the I agree... box. You can also use a Set Variable action to change its value at installation time.