If you find this confusing--especially the pricing and the minimal functionality--consider that ThoughtBot is a contract shop that also happens to package up some of their client work into side products and educational materials. They probably developed this as functionality for a client.

That's probably also the pattern with: "FormKeep is a form backend for your static sites. No need for iframes, JS embeds, and CSS overrides." https://formkeep.com/

Take the example of Pivotal Labs developing Pivotal Tracker for their in-house work and starting to sell it on the side over time.