Between Omicron Interactive, 0x97, and our teams, we have a lot of domains to manage. Most free DNS services either won't allow enough domains under one account, or they don't have several of the features we need. We didn't want to spend lots of money on a commercial service, so our solution was to deploy a set of nameservers on servers around the globe. Then, we realized we still needed a web-based management portal for our team to be able to quickly and easily make changes.
We discovered PowerDNS-Admin, an open-source application that did just that. However, it was lacking many features, so we forked it and expanded heavily upon it. We overhauled everything from the UI to the Python backend, adding dozens of features. We published our fork as its own open-source project, and continue maintaining it on out Gitlab server.