There are two ways to use AI for free within Novelcrafter.
Connect to OpenRouter, and use one of their free models. To see current pricing go to https://openrouter.ai/docs#models. As of November 2024, top models for writing include Toppy and Google Gemma. You will need to regularly check on OpenRouter's pricing to ensure the models are still free.
Run open source LLMs (from, for example, Hugging Face) directly on your computer via, for example, LM Studio or Ollama, and hook them up to Novelcrafter. You may find more specific information in the Novelcrafter discord under the following channels: Integration/#LM-Studio and Integration/#Ollama.