When installing SIMPSON on a Mac computer, you may experience the error that the program comes from a non-trusted developer. This is because we haven't teamed up so tightly with Apple that we have become a trusted developer team - only major software developers do this.
To proceed with the installation, you have to open the Settings > Security & Privacy, where you find the option to select installation of apps from anywhere. Select this option and install SIMPSON. After the installation, you can move back to a more secure setting if you wish.