MegaMek and Macs - MegaMek/megamek GitHub Wiki

Due to Apple's ever increasing security on macOS, some additional steps may be required. First and foremost, use the Linux package as currently there are issues with automation and dealing with Apple Notarization to work with Gatekeeper.

With the new security, Apple has additional precautions for ANY code in the Downloads folder.

After you unzip the contents of the package, move it OUT of Downloads to anywhere else. Our suggestion is the Users 'Applications' folder (generally /Users/username/Applications). If Java is setup correctly (either the official package or OpenJDK), you should be able to double click the Jar files and run them without any issue. If you have have further issues, please check here.