Firstly, your conclusion is incorrect, the free version of the plugin will put your EPN campaignID on 50% of links shown and the plugin author’s on the other 50%. This is to help fund the maintenance and upkeep of the plugin.
The Premium version is priced competitively and will ensure 100% of links shown contain your EPN campaignID. Thus you have a choice as to how you fund this plugin, with the ability to try it out with no outlay.
I’m sorry you feel this was enough to give my plugin a 1 star rating. Especially when the Freemium model is extremely common for WordPress plugins – providing a basic offering for no cost, and premium feature for a subscription.
Do also compare this with other plugins in this niche, e.g. Auction Nudge, which attributes 100% of all links to the plugin author with no other option. Or WP eBay Product Feeds which relies upon the RSSGround service that itself requires a paid subscription for all but the most basic of use.
