It's definitely weasel words. Open Source has a definition. The source may be publicly viewable, but that isn't "open". It's still closed, and it being viewable is actively harmful, as it'll lead to copyright violations sneaking into other projects.
Yea I understand that there's a technical definition that it falls short of, but again they're very explicitly noting that it falls short of that, so I don't see how it's being ambiguous or misleading. And I don't buy that it's not "open" - it's out there in the public; it's open for contribution from the public; it's open to be modified and deployed except if you're a monitoring provider. The OSI doesn't have a monopoly on the definition of the word "open".
Also I think that the assertion that it's "actively harmful" is wildly hyperbolic. Sentry isn't going to be out there copyright trolling people and you know it; they're trying to protect themselves from a very specific category of IP infringement. And there is still much potential upside to it's openness that you're willfully ignoring.
