Comment by AnimalMuppet

It will be enforced by $BIGCORP suing $OPEN_SOURCE_MAINTAINER for more money than he's got, if the intent is to stop use of the code. Or by $BIGCORP suing users of the open source project, if the goal is to either make money or to stop the use of the project.

Those who lived through the SCO saga should be able to visualize how this could go.