No. Only the main domain owner can install cgi-scripts that will run. Any cgi-scripts you wish to give users access to must be installed by the userid of the domain owner in there cgi-bin. Then the user can call them with the URL
The user (domain account extra users) login is slightly different than the master domain login. It requires that the domain the user account is on be used also. The proper login format would be
userid@domain.com
if the domain was "fred.com" and the extra user is "info", the login would be info@fred.com