Historically, not even the Open Source Initiative tried to define "open source" this way. There were licenses commentators agreed met their definition that they

Historically, not even the Open Source Initiative tried to define "open source" this way. There were licenses commentators agreed met their definition that they did not approve---open source but not OSI-approved. See also "license proliferation". There's also the whole issue of "public domain". Is CC0 code "proprietary"? And that's setting aside the more basic issues of whether an organization like OSI can impose its definition on the universe, whether the definition it's been trying to impose really works or just sounds good, and whether that's really a legal spec or a political document. The world is messy. It does not owe us the luxury of clear binaries.