@toast CC-0 was not approved but also not rejected, and most of the OSS lawyers I've talked to have said it's good but not for software.

I was mildly surprised that OSI goes so far as to say that you should not use "open source" to refer to anything except OSI-approved licenses ( https://opensource.org/faq#avoid-unapproved-licenses ). I would think that they'd be OK with you using the term "open source" to refer to things that meet the OSD (https://opensource.org/osd-annotated) but aren't approved for license proliferation reasons.