Is this a circle.io or similar software custom installation or was it developed by the n8n team?
@anbrudan
it’s not a CircleCI (or “circle.io”) installation; it’s a system and ecosystem designed and run by the n8n team, built around npm packages and the n8n-node tooling. The exact tech stack behind the community portal/UI isn’t described in the provided sources.
Good question 
n8n allows you to build and publish your own nodes as npm packages, which anyone can install and use inside their workflows. This is how many integrations outside the official node set are created.
If you’re interested in how the ecosystem is extended by the community, these are a good starting point:
https://docs.n8n.io/integrations/community-nodes/
https://docs.n8n.io/integrations/creating-nodes/