Strictly speaking yes, but as this thread shows, any actual attempt to do so will result in a storm of angry and mean developers looking for any potential flaw. Is absolutely every change available and documented? Did the repository go offline for an hour last Sunday night? You are allowed to sell GPL software like you are allowed to press your fingers into a meat grinder. If you actually look at big software houses you will find a majority avoiding or backing away from GPL code in favor of BSD or Apache style licensing because dealing with GPL is such a wretched nightmare for commercial entities.

I hear Linux is pretty popular. Oh wait, it's under the GPL. And there are multiple commercial organizations selling Linux distributions.

I'm sure no one uses the git Version Control System. Oh wait, that's open source software under the GPL.

Your assertions are easily proven false. Sure, a lot of organizations prefer permissive licenses, but saying no one does the GPL is absurd.

This is some hardcore FUD. Do you have any evidence to support any of this?

Apple seems to avoid GPL at all costs and was presumably the reason why macOS used to ship with an older version of gcc (and related tools?) due to the older version using a more permissive version of the license.

AFAIK there could also be some issues sending software to the AppStore if it includes GPL licensed code, but LGPL licensed binaries should be ok to include (from what I understand). Of course this is from a closed source standpoint, my clients don’t generally like to open source their projects.

Personally GPL sounds like a minefield to me so as a developer I avoid GPL licensed code if possible and much prefer BSD licensed code.

Ah, well that answers that.

I still feel like the asset flipping issue is a legitimate concern though.

To expand a bit on what the parent said: you're allowed to sell GPL software, but the person who bought it is still welcome to give it away for free. The FSF is of the opinion that this can be a viable business model, but I'm not sure I believe that.

Once I heard there was a company called Red Hat...

There's been cases of people taking Blender, renaming it and selling it as their own "3D authoring software". GPL permits that, although morally it's very sketchy.

If the people selling it are providing support for it I don't really find it morally sketchy. Especially if the provide credit- which is required by many open source licenses, in one way or another.