Is there a popunder script that works as good as popunderJS?

[backgrind]

Trying my luck - Just found out about https://popunderjs.com/demo/demo.html

Looking for code access to self-hosted popunder script that I can use.

PopunderJS a bit pricey and I'm aware of Luke's Backunder. I'm looking for the source JS code.

The script from network usually makes the popunder active which