They'll definitely be required to either add the attribution or stop using the code.

There can be punitive fines for copyright violation, moreso if the copyright is registered. I think there's some leeway there for the court.

There also may be damages. In the case of, for instance, illegal distribution of a Disney movie, Disney may be entitled to the amount of sales they supposedly lost.

It makes me think that open-source projects should routinely offer their product for sale, without the attribution requirements. Then, if another company violates their license, they have a tangible dollar figure they can point to and say exactly how much revenue was stolen.