GPL version 3 explicitly says "you may charge any price or no price for each copy that you convey". The MIT license also explicitly allows selling the work.
No other free or open source license forbids selling either. In fact the Open Source Definition from OSI expressly says: "The license shall not restrict any party from selling or giving away the software as a component of an aggregate software distribution containing programs from several different sources."
Linux distributions have been commercially sold for decades. Red Hat built its entire RHEL business on that, even when they still played nicer with open source. (Of course the key really was the support they provided to their paying customers but I think you still needed to pay to get your hands on RHEL anyway.)
Of course the problem you'd be facing if you wanted to sell free software at a significant price would be that since you can't forbid redistribution of the copies you sold (and you need to provide source code), someone else can take what you sell and redistribute it for free. So you can only really sell other people's free software if you either get ignorant people to buy it despite the same thing being available for free elsewhere, or if you provide something else on top of it that people are willing to pay for.
That severely limits the possibilities of making big bucks by just selling free software developed by others.
Perhaps the community is philanthropic to the point of providing free software for other people to sell. But the community or the authors of the licenses aren't naive. The possibility has been known from the start, as was the fact that it's after all quite difficult to charge a lot of money for selling something when free downloads are also almost guaranteed to exist.
I'd be a lot more concerned about how volunteers assume active maintenance burden and responsibility for software libraries that are used for free by just about every software company on the planet.
I don't see anything about trinsic2's (or anybody else's) promoting Linux or installing it on customers' computers that would be in contradiction with open source, even morally. I certainly don't see how a "license" could be required for doing so when the individual licenses of each included piece of software already permit commercial distribution. The only way he might need a separate license would be if he installed a distribution that's actually not entirely open source and bundles proprietary components that are not freely distributable.