The default settings of MacOS Sierra security system do not allow to run applications made by a developer who is not identified by Apple.
If you double-click such installers, you will get the following message: “XXXXX” can’t be opened because it is from an unidentified developer.
In order to install and use our dictionaries, right-click (or Ctrl+click) the installer instead of double-clicking it, and choose Open from the context menu. You will get the same message as before, but this time an Open button is present.
Click the Open button: the system will remember your choice for this application.