It's open source in the sense of OSINT [0]. Clearly confusing on a site like Hacker News, but this has been standard usage of the term for that community for a long time now.
Thank-you for the clarification. "Open-source" is definitely different from "Open Source."
Meaning Open-source (sourced from open sources) but claiming Open Source is disingenuous.
Wikipedia isn't helpful either, because it refers to OSS as Open-source Software [1].
Open Source meaning may be more useful in comparison to Free Software. Stallman refers to "Open-source" (hyphenated) only once in this article, but only to refer to it as confusing versus free software [2].
It's possible "OSINT as Open-source" has been in use for longer than Stallman's use of "open source," but definitely they are different.
It's strange a site would sell up a feature on HN as "Open-source content, in the meaning of OSINT" without being up-front about it. The default assumption would be "open source as code that is free to modify, etc."
The mental gymnastics would be
1. They claim it is "open source."
2. They are talking about _content._
3. It must be the OSINT kind of "open."
This could be a pattern, because they're always needing to add another comment, "Just kidding, we meant OSINT open; we're not sharing the code."
... documentation could be open source too, though--in the sense of "free to modify, etc" and not "sourced from freely available data."
Could it be both? Only if they accept contributions, I guess.
0. https://en.wikipedia.org/wiki/Open-source_intelligence