I think the title of this article is misleading. This is an agreement between Id and ZeniMax not ZeniMax and Oculus. The implication of the article is that Carmack violated this agreement (he didn't sign this agreement Id's lawyers did) and didn't negotiate an exception for Oculus in the same fashion as he had for Armadillo Aerospace
Edit: For clarification I don't think Oculus "broke" this agreement, perhaps Carmack did though.