Do I need a Perplexity, DeepL or OpenAI key to use BookyAI?

No. They are optional and each one serves a single feature. You find them in Settings under "Extra tools". Covers: an OpenAI key gives the best AI covers; without it covers use your free Gemini key. Translations: a DeepL key adds DeepL as a second translation engine; without it your AI engine translates. Fact-check: a Perplexity key is used only by the fact-check in the editor. Writing, editing, exporting and everything else work without any of them. To write books you need one writing engine from "AI engines": the free Google Gemini key is enough.