If you want to know how the 10th Circuit, which is the circuit Utah falls into, defines derivative code, you can read Dan Ravicher, Esq.'s paper, "Software Derivative Work: A Circuit Dependent Determination." [PDF]
According to this analysis of the different definitions the different federal court circuits follow, the 10th Circuit follows the AFC test, abstraction, filtration, comparison:
Under the AFC test, a court first abstracts from the original program its constituent structural parts. Then, the court filters from those structural parts all unprotectable portions, including incorporated ideas, expression that is necessarily incidental to those ideas, and elements that are taken from the public domain. Finally, the court compares any and all remaining kernels of creative expression to the structure of the second program to determine whether the software programs at issue are substantially similar so as to warrant a finding that one is the derivative work of the other.Details on each step of the process are in the article.
Often the courts that apply the AFC test will perform a quick initial comparison between the entirety of the two programs at issue in order to help determine whether one is a derivative work of the other. Such an holistic comparison, although not a substitute for the full application of the AFC test when, as discussed below, only certain components of the original program are compared to the second program. If such a pattern is revealed by the quick initial comparison, the court is more likely to conclude that the second work is indeed a derivative of the original.