It’s actually very clever of him. He knows you want free, and so you will at least try his plugin. If for some reason it doesn’t suit you, he already knows that the largest portion of “paid plugins” sales for a forms plugin is Gravity Forms, so he puts he affiliate link in there so he will make a buck or two off of your purchase from a competitor.
Notice the links have either “&aff=125082” or the other “&afftrack=” which indicate they are his affiliate links. Don’t hold it against him though for using that space in the settings to try to recoup some money for his time. How is he supposed to eat when he gives his plugins away for free?
The plugin itself is great though, and I’ve found it quite useful.
I wouldn’t even consider holding it against him, it is a clever scheme, and I appreciate that. I simply wished to note how insecure it made me feel.