Actual behaviour:

When you click on the link in the course, it takes you to a useless page, which then tries to open the pop-up window on-load. This is exactly what pop-up blockers block.

Expected behaviour:

When you click on the link on the course page, a pop-up window opens and loads the external tool. Your original browser window is left looking at the course page.

(Like when a Page is set to open in a new window.)