You can try out the 345M-parameter model in your browser here https://talktotransformer.com. The more powerful models are available to AI/security research groups upon request.

You can, see: https://github.com/openai/gpt-2/blob/master/DEVELOPERS.md.

But this is for a smaller version of GPT-2 (~400M parameters). Since the bigger model (2B parameters) was deemed too dangerous by OpenAI.

GPT-2