Also, simply making the source-code visible to all, helps keeps the honest guys honest. That's true even if the licence isn't truly Free and Open Source.
No-one dares to commit spyware to GitHub.
No-one dares to commit spyware to GitHub.
I see where you are coming from, but this is simply not true. You can argue nobody concerned with his own reputation commits spyware to a public repo, but malicious actors are usually not concerned with that or try to stay anonymous in the first place.
Here is a recent example of malicious commits to a github repo: https://news.ycombinator.com/item?id=17458329
It's not so black-and-white though, hence "keeps the honest guys honest". Are Microsoft and Google 'malicious actors'? They're hungry for our data, but they often only do it when they don't think we'll be able to find out what they're doing. https://news.ycombinator.com/item?id=17749330