One extra step the first time you open it — here's exactly what to do.
When you open the downloaded .pkg, macOS will block it and say
it's from an "unidentified developer" or that it "cannot be
opened because Apple cannot check it for malicious software." That's
expected — it's not a virus warning, and it's not specific to your Mac.
Follow the steps below and it opens normally.
Find Coursepad_…_universal.pkg in your Downloads
folder and double-click it. macOS will show a dialog blocking it from
opening.
Click the Apple menu in the top-left corner of your screen → System Settings.
In the sidebar on the left, click Privacy & Security.
Near the bottom of the page you'll see a message that Coursepad was blocked, with a button next to it: Open Anyway. Click it.
A popup will ask you to confirm. Click Open Anyway again, then enter your Mac login password or use Touch ID if prompted.
Go back to the .pkg file and double-click it one more
time — it will now open normally. Click through the installer; it puts
Coursepad in your Applications folder.
Open it from Applications or Launchpad, same as any other app. You won't see this warning again on future updates — the installer clears the flag for good.
.pkg file and choose Open
from the menu, then Open again on the popup — this skips
System Settings entirely. If that option doesn't appear or doesn't work
on your version of macOS, use the Settings steps above; they always work.