System requirements: Mac OS X 10.10 or higher, with Java 1.8 or higher required. (Java 1.8 is also called Java 8.) Mesquite may or may not run on older systems.

Instructions:

If you have an older version of Mesquite, you may want to delete it (by deleting Mesquite_Folder), so as to avoid getting confused as to what version of Mesquite is starting up. First, however, you may want to take from Mesquite_Folder/mesquite any third party packages (e.g., PDAP, TreeSetViz) before deleting the directory.
Download the latest version of Mesquite from the Mesquite Github repository.
If the downloaded file doesn't mount into a disk image automatically, double click it to mount. You will see a Mesquite_Folder. Drag this Mesquite_Folder to your hard drive (e.g., your Applications folder). Its contents should be approximately as follows:

Mesquite_Folder
- com/
- corejava
- documentation.html
- edu/
- examples/
- images/
- jars/
- lesser.txt
- lib/
- mesquite/
- Mesquite_Starter.app [There will be several different versions of this, with slightly different names]
- Mesquite_Starter_INSTRUCTIONS-macOS.txt
- mesquite.jar
- org/
- RunningOptionsForFlex/
- settings/
- start/

Double click one of the Mesquite_Starter icons to start Mesquite. If you don't have Java installed, you may be asked to install it.
Which Mesquite_Starter should you use? We offer several different versions because the diversity of macOS versions and Java versions make it too challenging to provide you a single solution. The different versions of Starters also provide different amounts of memory. Try them, and see what works.
For more complete instructions about starting Mesquite and what can go wrong, see the file Mesquite_Starter_INSTRUCTIONS-macOS.txt.

More details of issues of using Mesquite under Mac OS X are described in the Support page.
(Please email us (info {at} mesquiteproject.org) with questions or comments about downloading Mesquite).