A friend of mine, who develops with Qt, always archives his projects as a VM. Once he needs to work on it later, he has all the tools etc. in place to continue where he left it.
I would highly recommend to leave the terminal alone and not disable gatekeeper. It protects you from accidentally launching an app looking like a movie or image file!
For Bob’s problem, you can of course check and remove extended attributes, remove broken code signature or delete quarantine database if needed.
Better use a VM with an older, compatible version such as Snow Leo, than damage Sierra to have it run an antiquity…