Did ZZT allow consumers to use other programmers' programs on their programming system so that these other programs could be run within ZZT or was the ZZT platf

Did ZZT allow consumers to use other programmers' programs on their programming system so that these other programs could be run within ZZT or was the ZZT platform an unethical and walled garden? Was the walled garden an antitrust violation? Why were other "app stores" not allowed?!