Although Morris claims he did not intend to release the worm as a malicious act, merely as a research project, the very fact that he disguised its origin by releasing it from MIT rather than his own school, Cornell, suggested that he knew that what he was doing was wrong. Although one could argue that the damage it caused was due to unintended consequences, Morris fails Kant's ethical tests in several ways.
First, the categorical imperative requires that one always universalize one's maxim. Thus Morris would have needed to consider what would have happened had every internet user released worms, and think about how the increase in traffic would disrupt the internet.
Next, Kant requires that we consider every intelligent being as an end in itself rather than as a means to an end, which would require that Morris consider the effects of his action on other people before acting, which he did not.
Final, Kant requires that we consider duty before committing an act that might have moral consequences, and Morris failed to do that.