Cobertura is a reporting tool for code-coverage of unit tests.
The license for Cobertura is complicated: Ant tasks are covered under Apache 1.1 (easy enough), but instrumented bytecode involves the GPL.
Details are here: http://cobertura.sourceforge.net/license.html
In a classic CYA, the conclusion of the license states "it depends on your interpretation of the license".
How have you interpreted the license?
Do you use Cobertura in developing commercial software for the enterprise? i.e. simply using it to report on your JUnit tests. I'm not asking about bundling Cobertura with your product.