It did not state any consequence

I don't think it will affect your greencard--since the Company would not have any Legal basis for that. However, if you break it, then the Company might sue you for "somthing"--which is not defined here (in your quotation), so it might come up with the details when it sues.

I am not even sure whether a company can legally put out something like this.

If I were you, I would take the other job--it is too fishy.