"Hypothetically, similar efforts taken by others to reverse-engineer Microsoft Windows could be deemed justifiable if the aim of those efforts were to make other companies' programs, designed for Windows, run on an operating system other than Windows. This assumes that the 9th Circuit ruling holds up."
http://www.planetit.com/techcenters/docs/security/news/PIT20010123S0001/1?spsubcat=bugs_flaws