n8n (a numeronym for “nodemation”) is a node-based workflow automation tool. The reason for the square quotes around “open source” is because it has a Commons Clause attached to its Apache 2.0 license, which means you can do anything you want with the source code except make money with it. Since n8n itself is built on open source tech such as TypeScript and Vue.js, this is a nice touch by the author in the FAQ:
As n8n itself depends on and uses a lot of other Open Source projects it is only fair and in our interest to also help them. So it is planed to contribute a certain percentage of revenue/profit every month to these projects. How much exactly is not decided yet.