If it were a gatekeeper issue the warning would be issued on installation or in some cases an option would be offered to override gatekeeper protection on execution, but no such option is offered in this case. The application is refusing to run because of an invalid code signature with no gatekeeper override offered.
"All you've got to do is own up to your ignorance honestly, and you'll find people who are eager to fill your head with information" --Walt Disney
