From the project's page https://github.com/openai/gym:

> The team that has been maintaining Gym since 2021 has moved all future
> development to Gymnasium, a drop in replacement for Gym (import
> gymnasium as gym), and Gym will not be receiving any future updates.
> Please switch over to Gymnasium as soon as you're able to do so. If
> you'd like to read more about the story behind this switch, please check
> out this blog post.

Gymnasium is successor of Gym.
Closing as not actual. 

Thanks,
Oleg