How to periodically show alert message *in foreground*?
Try using open instead of launching the program directly. open more closely matches double-clicking to launch the AppleScript application.

open your application

To do this, replace the Program key value pair in your launchd job ticket with a ProgramArguments array to provide the path to your AppleScript application:

&lt;key&gt;ProgramArguments&lt;/key&gt;
&lt;array&gt;
    &lt;string&gt;/usr/bin/open&lt;/string&gt;
    &lt;string&gt;/Users/bernhard/programming/periodic.app&lt;/string&gt;
&lt;/array&gt;


By default, the open command attempts to bring the launched application to foreground.