The fork may still contain some components which are not covered by the GPL. For example, if a new file was added to the fork by the distributors, then the dist

The fork may still contain some components which are not covered by the GPL. For example, if a new file was added to the fork by the distributors, then the distributors control the copyright to that file, and the viral nature of the GPL does not kick in. You'll have to be careful to vet each file, with respect to any GPL'ed version, to see if the differences are covered under an unacceptable license.