EmailEngine

EmailEngine began as an open source project shared freely under the AGPL license. The creator believed in the power of open source and wanted to contribute to the community, but also offered a paid MIT license option for those who preferred commercial freedom. This dual licensing model seemed reasonable in theory—users could either accept AGPL terms or pay to opt out.

The creator built a functional email engine and released it into the wild. For anyone wanting to use it commercially or avoid open source restrictions, a MIT license was available for 250 euros per year. It was straightforward, permissive, and seemed like it should work.

But here's where things got stuck. After a year and a half, the creator had generated only 750 euros in total revenue. That's an average of just 500 euros per year. People weren't buying licenses. They were either using the free open source version or simply not using the tool at all. The honor system wasn't working. The creator had built something useful, but nobody was paying for it.

The breakthrough came when the creator implemented a crucial enforcement mechanism: requiring a valid license within 15 minutes after the app started. If you didn't activate a license in that window, the app stopped working. This wasn't aggressive—it gave a grace period—but it was unmistakable. You couldn't accidentally ignore payment. Suddenly, the model shifted from "please donate if you find this valuable" to "you must pay to keep this running."

This single change transformed everything. Rob Walling noted that the creator had essentially implemented "what we would think of as a time-limited SaaS trial," converting a donation model into a mandatory subscription requirement. Users who wanted the tool had to engage with the payment process, not as a nice-to-have, but as a necessity.

The results speak for themselves. Current MRR stands at 6,100 euros, growing steadily. The creator has continued raising prices incrementally—from the original 250 euros to 495, then 695, 795, and finally 895 euros per year. Anar Volset even suggested the pricing could go higher ("try that with a zero and see how that goes"). In Estonia, where the creator lives, this recurring revenue provides a comfortable full-time income. What started as an undermonetized open source project became sustainable through a simple but decisive change: making payment unavoidable rather than optional.