Linux was originally under a similar license. It could have died in the same way, leaving only the BSD projects, which have been much less effective at attracting contributors. You could argue that maybe without competition from Linux, they would have been able to attract more contributors; but I think the truth is the opposite — with fewer free-software users, there would be fewer free-software contributors, and less free software, increasingly marginalizing free-software systems.
And, without inspiration from Stallman's ideology, even BSD would never have become free, according to Keith Bostic.
So we'd have some free software, but we wouldn't have a coherent movement that strives to ensure that everyone can use a 100%-free-software system.