by Jason Hardin.
You can add an external tool that allows you to add content from that external toll to any course. This is done at the site level under plugins > activities> external tools.
This just lets teachers add content from the external tool to the course. There isn't a way to add a specific activity to every Moodle course. The best method I know is to create a master course with the resource and then create all courses from that course. You will have to manually import the activity into existing courses.