It may not be "Free Source", but if the source is open in the sense if being accessable, then for normal people it is open source. One organization using words in a specific way, doesn't negate all other legit interpretations of those words.
Nope. Open Source is a trademark precisely to avoid this sort of misuse. It's not a "what it means to whomever" sort of deal.
That was done in part due to intentional (and damaging, if ultimately unsuccessful) efforts to undermine the meaning of terms like 'Free Software' by Microsoft back when the FSF was a fledgling movement and Microsoft was an evil empire.
I don't mean to imply negative things about the company. The license is still a heck of a lot better than fully proprietary -- I love the product in part for that reason -- but it's definitely not 'open source' or 'free software' as the headline implies.
I'm talking about casual language-usage, like this headline, not commercial usage. Open and source are regular words, and they still are regular words when used together. Trademarks can't force people to talk as they want, it can only force company to not sell everything as they wish.
Yes, the term can't be trademarked, because they're both common English words used in combination (and that combination has a somewhat older, unrelated meaning, which further contributes to making the term untrademarkable).
But this isn't a trademark issue. No one has trademarked the word "carrots" either, but if someone were to sell pencils under the label "carrots", people would be understandably confused and annoyed.
It's the same thing here: don't call it open source if it's not. The software industry relies on that term having a specific, well-defined meaning. That meaning is widely agreed on, which, again, is why Numworks themselves is not claiming their stuff is open source.
Well, sure, language is ultimately defined by usage, so if enough of us agree that the word "broccoli" refers to source code being available, then it's legitimate to go around saying "broccoli" means "visible source", etc.
But the important question is, who is using "open source" to mean the definition I gave earlier? The answer is: pretty much everyone. Not just the Open Source Initiative (opensource.org) and the Free Software Foundation, but also: the Wikimedia Foundation, Creative Commons, the Electronic Frontier Foundation, all government agencies who have formally defined the term (at least as far as I've seen), also every major tech firm as far as I can tell, including Google, Microsoft, Amazon, Apple, IBM, Hewlett-Packard, Yahoo, Samsung, Huawei, ... this list could go on for a very, very long time :-). Basically, it's everyone.
Notice that that list includes Creative Commons -- that is, the organization that wrote the particular license that Numworks is using agrees that that license is not open source. That's a pretty clear sign, I think :-).
And, of course, Numworks themselves are careful not to call their stuff "open source" anywhere. You can bet that they would use that term if they felt they could. It has great marketing karma; everyone loves to advertise their stuff as "open source". And yet Numworks doesn't -- because they know a lot of hackers would come down on them like a ton of bricks if they tried to make that claim.
To a first approximation, pretty much every organization that produces or procures software use the term "open source" to mean the definition that the Open Source Initiative originally established.
You can claim that "open source" means something else, if you want, in the same way that you can claim that the word "broccoli" or "red" means something different from what most other people mean by those words. For you, your meaning will be correct, in your own private language.
But what I'm saying is, when the phrase "open source" appears in a Hacker News headline, most people will interpret it in the way I described. When the vast majority of people intepreret a word or phrase as having a certain meaning -- and especially when it's a term of art in a profession and all the specialists, lawyers, policy makers, etc in that profession agree on the meaning of the term -- then it's fair to say that that is what the term "means".
Open source is a technical term (and I believe a trademark) with a specific meaning, defined by [The Open Source Initiative](https://opensource.org/). It does not merely mean that the source is available. As you hint at, being free software is a higher requirement, but this does not meet even the lower requirement of being open source.
It's an unsolvable problem they created there.