WriteMapper 3 works on macOS and Windows.
Do note that on a Mac, it requires macOS 10.11 (El Capitan) or newer in order to run. On Windows, it requires Windows 7 or newer; older operating systems are not supported (and do not work).
On WriteMapper 2 for the iPad and iPhone, iOS 10 and above is required for WriteMapper to install and run, with iOS 11 or newer highly recommended to take full advantage of the features integrated into the WriteMapper 2 app.
Please refer to this article for more information on future availability on other platforms and operating systems.