You can run ExtendSim on a Macintosh computer, just not natively. ExtendSim is a Windows application, but there is a way to run Windows applications like ExtendSim on Macintosh computers.
Solution -- Install Windows 10 and an emulator on your Macintosh. To do this, you need to obtain the Windows 10 operating system and install it on your Mac. For the emulator, you can use Boot Camp Assistant (installed with the Mac OS in the Utilities folder under Applications) or install the emulation software Parallels (www.parallels.com). During installation, the emulator will request the Windows OS installer to complete the process. Once the installation of the Windows OS is complete, boot the Windows OS, install and activate ExtendSim, and start modeling!
Note: The Trial version of ExtendSim does not run on a virtual machine (VM) and a Mac running the Windows operating system is considered a VM. You can install the Trial version on a VM, but in order to launch the software you must activate it using an Activation Key or, in the case of a Floating license, a license file from your ExtendSim License Manager.