Unfortunately the term "open source" as used by many people is not necessarily synonymous with the official OSI definition available here.
The OSI definition is for most intents and purposes equivalent/compatible/similar to the FSF definition of "free (as in freedom) software" available here
https://www.gnu.org/philosophy/free-sw.htmlFor an official example of the use of the term "open source" to mean "you can read the source but are not allowed to do anything else with it" see the 2007 announcements about QNX. OSI explicitly declared there is no (OSI) open sourcing in what QNX did at the time. https://opensource.org/node/195
For an example of people using the term to mean only "you can read the source" look no further than the discussions related to the recent leaking of Amiga 3.1 source code where people were debating if an effort can be made to convince the copyright owners to "open source" the code:
"Correct me if i'm wrong, but open source doesn't have to equal FOSS. I'd be inclined to agree with you if it were FOSS, but just being open source could provide 'assistance' to Cloanto who can incorporate peoples ideas/fixes but still retain the right to sell it when others don't. Managed well, could it actually be beneficial to Cloanto and the broader Amiga community?"
"You are correct. FOSS and Open Source are not the same. Permissive licensing doesn't have to be attached to the opened source."
"This is true, but nobody suggested it should be FOSS, me included.
Open sourcing of any kind just isn't going to happen without some sort of miracle."
Unfortunately the term "free software" is a terribly ambiguous one (and Richard Stallman and the FSF are to blame here since they knew about the homonimity of the word "free" beforehand)
And even more unfortunately "open source" has for a long time become ambiguous. You can not rely on "open source" meaning "OSI open source" to everyone you talk to.
And members of both organisations and their supporters spend a lot of time fighting about the meaning of each others terms.
So we are stuck with the horrible term "FLOSS", an abbreviation of "Free & Libre & Open Source Software" to roughly define what we actually want to talk about: both copyleft ( https://www.gnu.org/copyleft/ ) and copyfree/permissive ( http://copyfree.org/standard ) licensed software (and in some cases also public domain).