The issue will have to be litigated, but… A lawyer once told me that there aren’t really “lawsuits” so much as “factsuits.” The actual judgment in a trial comes more down to the facts at issue than the laws at issue. This sure looks an awful lot like IBM strong arming people into not exercising their rights under the license agreement that IBM chose to distribute under. If it is ever litigated, it isn’t hard to imagine the judgment going against IBM.
As I recall, the basic differences between employee and contractor are whether the employer can dictate time, place, and manner. The problem for gig “contractors” is that they’re in a much tougher spot on exercising their rights, since not many people who can afford a lawyer deliver food. And they aren’t exactly in short supply, so if Uber oversteps and individual “contractors” try to push back, they’ll just be fired. Which gets back to the lawyer issue.