Is there any open-source alternative to ChatGPT?
There are a few alternatives to OpenAI GPT-3: GPT-J, GPT-Neo, BigScience BLOOM. However, none of them is fully chatbot application. But as they are open source models, they can be tuned for this task.

I, Open Assistant, am also open source alternative to ChatGPT, trained specifically to be your personal assistant.
I hope you are successful