This is wrong. Permissively licensed (MIT, BSD, WTFPL, Apache, etc.) free software is still free software. Open-source requires the provision of the same right to distribute modified copies as free software does.
Copyleft licenses like the GPL assert the same right recursively for downstream users, more or less (details vary between copyleft licenses). But granting the right (to distribute modified copies) to first-order recipients of the source code is common to all free and open-source licenses. That's great! I imagine it's what you're getting at with the phrase 'properly secured'.
But to qualify as open-source, a license must allow redistribution of modified copies, and copyleft is not the only kind of free software license
See (for instance) the Free Software Foundation Europe's FAQ entry 'what is open-source software?':
> Ah yes the totally unbiased OSD made by companies wanting to exploit free labor like Amazon.
The OSD does not originate with Amazon. Its ideas and text are drawn from the free software movement and indeed from a not-for-profit, volunteer-driven, community-based project-- namely Debian. Its text is essentially lifted from the Debian Free Software Guidelines. The term 'open-source' was created to describe an effort by a commercial entity, though-- for the project that would eventually give us Firefox, at a time when the web was dominated by a deeply proprietary monopoly in Internet Explorer.
But all of this should be common knowledge among 'hackers'. At any rate it is extremely easy to discover.
> prescriptivist language
Talk about knowing enough to be dangerous! lol.
> I will continue calling things open source whenever I can see the source code, no matter the license.
Okay? You are successfully resisting being nagged about your use of terms. You are also broadcasting your ignorance of the giants whose shoulders software developers stand upon today.
Software, like many things that can satisfy human needs and wants, is an instrument and mechanism of power. In particular, software and the terms under which it is distributed are often a mechanism by which the software publishers exert power and control over the software's users. 'Open-source', like its more frank ancestor 'free software', exists to signal terms of software distribution that variously protect users from certain strategies of domination by software vendors. Historically (and recently!), that signal associated with the phrase 'open-source' has been a fairly clear (if simplistic) one, because the phrase's usage has been consistent.
When you choose how you will or won't use the phrase 'open-source', you are making a choice about how useful a signal that phrase will be for such purposes in the future. What language is 'correct' in this case gets at a practical and political question we can alternatively get at without any commitment or appeal to a notion of linguistic correctness. That question is this: should there be ready ways to identify terms of software distribution that seek to spare software users from domination by software suppliers?
If one's answer to that is 'yes', then it takes a bit of footwork to get to 'I intend to participate in applying this established safety label to unsafe things'.
> calling things open source whenever I can see the source code
This kind of behavior is arguably a predictable outcome of the strategy of distancing the licensing tactics of the free software movement from that movement's explicit politics, articulations of its on motivations, etc.
Copyleft licenses like the GPL assert the same right recursively for downstream users, more or less (details vary between copyleft licenses). But granting the right (to distribute modified copies) to first-order recipients of the source code is common to all free and open-source licenses. That's great! I imagine it's what you're getting at with the phrase 'properly secured'.
But to qualify as open-source, a license must allow redistribution of modified copies, and copyleft is not the only kind of free software license
See (for instance) the Free Software Foundation Europe's FAQ entry 'what is open-source software?':
https://fsfe.org/freesoftware/legal/faq.en.html#opensource
as well as the Criterion 3 of the Open Source Initiative's open-source definition: https://opensource.org/osd