I built my own editor on top of the API, which I ran at home, yeah. You can see the code and/or run it yourself at https://github.com/indentlabs/gpt-3-writer, but it's very rough and not really ready for public use. Just make sure your OpenAI secret key is set in ENV['OPENAI_SK'] and you should be able to run it yourself.

I also built a more polished version to add to the Notebook.ai document editor (so writers can get some continuation prompts whenever they get a bit of writer's block), but the pricing made it unfeasible to actually release. Notebook.ai is also open source though, and you can see the GPT-3 functionality in the unmerged PR here: https://github.com/indentlabs/notebook/pull/739