Why is this here if it is free on steam? Isn't there like a rule that you can't request games that are already free.

Not only is this game free, its also available online; https://danielyxie.github.io/bitburner/
And if that doesn't float your boat, the full sourcecode is on github; https://github.com/danielyxie/bitburner

Why is this here?

Its also a really fun game, its kind of an idle incremental in the way that you need to make actual JavaScript files to automate "hacking".
The game goes pretty meta as well where people have made full GUI Shells for the game.
Basically if you know what you're doing you can change anything about the game, all from within the game and you even get achievements and rewards for it!
Game documentation: https://bitburner.readthedocs.io/