NOTE/UPDATE:An ARES Commander 2018 update (Build 126.96.36.19936) for the MacOS X Mojave that addresses this issue is already available under:
To Run Older ARES Commander Versions before Build 188.8.131.5236: Previous versions of ARES Commander don't work under OS X Mojave after installation. ARES Commander customers shouldn't upgrade their existing operating system directly to Mojave (which is for free for El Capitan or higher), because there is a crash at the first start of the application and a Fixed-UI-Mode issue with a flickering graphical area. Reverting from Mojave to the previous Mac OS X operating system version is also difficult.
Workaround for Older ARES Commander Versions:If a customer had already installed Mojave then we have a workaround. Before the first start of the CAD application customer has to add it to the Privacy exceptions dialog (Allowed Apps) under Security&Privacy settings.Then the application starts without any issues. Further, its recommended using the Mac-UI-mode (command UIMODE).