According to the Discord, Claude 3.5 Sonnet and OpenAI GPT-4o. Also according to the Discord, "SPRING (SG) PTE. LTD. or one of its affiliates" is fully subsidizing the costs. This doesn't look like a bring your own keys type of deal.
If it's truly talking to OpenAI or Claude, then the traffic can be intercepted and redirected to your own AI router for other cloud AI providers or your local Ollama instance.