arjaybe, my turn to be picky
. I believe the way you using the phrase "Free Software" suggests you are referring to software promoted by the Free Software Foundation, but this is quite restrictive. (And not entirely helpful.)
There is a lot of free software that is not open source at all, and there is a lot of open source software that does not follow the policies of the FSF.
Note, too, that there exists open source software that is not free. In software development it is common to have to pay a licence fee to gain access to the source code to libraries that I want to use. (
Such products are, obviously, not FSF or OSS software products, but are still "open" in the sense that anyone willing to pay the fee can read and modify the source within the licence imposed constraints. I will not develop using third partly software unless I have access to the source, but I do not limit myself to FSF or OSS.)
But it is fair and appropriate to be cautious of free software -
whether or not it is open source! (In fact, it is fair and appropriate to be cautious of non-free software too - since paying money is no guarantee of satisfaction.)
Not everyone has the expertise to assess the source, or, even when we do, do not have the time to study in detail the source code for all the software we want to use. So even if a product is open source and free you need to be comfortable with the provenance before deciding to use it. For most people that means staying with products or developers that are fairly well known and widely used.
My conclusion is that making a careful assessment of the provenance of a product is of more use to most people than whether a product is open source.