The key issue is whether the defendant's actions were a breach of contract or a copyright infringement. The court found that the License is a contract and the requirement to include the notices was not a restriction of the scope of the license.
In contract law, the preferred remedy is money damages, not injunctive relief. In copyright law, there is a presumption that injunctions are appropriate to stop the continuing violation of the license.
Thus, the question of whether the violation of a license is a contract violiation or copyright infringement (it can be both) is very important, because licensors would prefer to obtain an injunction prohibiting the breach of the license. ... The most celebrated case dealing with this issue involved the Java license between Sun and Microsoft in which the court found that the obligation on Microsoft to meet the Java compatability tests was a covenant, not a restriction on the scope of the license and the court denied Sun an injunction on those grounds (Sun got an injunction for unfair competition).
Here, the court found the restriction was a covenant, not a restriction on scope and denied the injunction. Says Radcliffe:
I believe that this decision is simply wrong. The use of the term "condition" in the Artistic License should mean that the terms imposed are restrictions on the scope of the license. In fact, the judge in the Sun case even noted that restrictions are provisions which use language such as "subject to" or "conditional". This decision, if upheld, will remove an important (and expected) remedy from open source licensors.
Note that this decision doesn't impact GPL directly, as it was addressed to the Artistic License; however, if the decision is upheld on appeal it will have precedential effect and may be applied to more open source licenses.