It looks like it is, but is there any official word that the SSPL is proprietary? As far as I know MongoDB claims it isn't, and it hasn't been reviewed officially by either the FSF or the OSI. Is it in license purgatory?
Bruce Perens feels “it manifests a lot of ignorance about Open Source and utter contempt for our community.” https://opensource.org/LicenseReview122018
The reaction on the OSI's license-review list is more varied. Lawrence Rosen and Ken Mitchell argue that the license should be approved. Everyone else is criticizing that it clearly violates the spirit of Open Source software (no discrimination against fields of endeavour!), and that the license is too broad and too vague in the critical section (Rosen agrees with the latter part). Carlo Piana points out that the goal of the license seems to be to create so much legal uncertainty that any serious user would be forced to buy a proprietary license from MongoDB.