We have a special way to run an Applet as a single file, but it is not possible to run a project with an applet. It
should be possible to set an Applet class as the main class and then run the project using the applet viewer the same
way as a single file.
There's a "workaround" - to setup WebStart for the project and configure it to use the applet - then the project is run
as an applet (local Web Start execution). But this only works if a main class is set - will file another issue for that.
Regardless the Web Start setup, a plain Applet project should be executable from the IDE as well.