Paypal popups caused by dashboard widget

On a site I’m starting to maintain, PDF Poster is installed, but every time I load the site’s dashboard, links are automatically opened to a paypal.com address.
It’s mostly blocked by my security software, but it looks like it’s tracking the usage and tries to collect donations. It’s related to the gumroad-embed.js file (in your plugin).

Can you explain what this is doing and why it’s opening the extra tabs? I didn’t opt-in for tracking or have the ability to turn this off, so I doubt if this is even allowed.