He says that "John Carmack’s GPL engine dream" is dead, but I'm not sure what that is. He doesn't provide any argument to claim that making games with Open Source engines is dead, he only talks about the now old Quake engines.
He claims that more games used the commercial Quake licence than the Open Source licence (I don't know if that's true), but surely, the commercial Quake engine was also "under-documented and relatively arcane. Perpetual bugs and lack of tech support are another."
This isn't an issue of "Open Source is bad, commercial engines are well documented and supported", because those same engines started out as commercial engines! Rather, it's more that Unity has come along, and is better documented and supported than anything else out there.
Does this mean that making games without Unity (Open Source or not) isn't feasible? Hardly, since plenty of games are still done without Unity, and we managed before Unity came along. Although I can see that a lot of people will be tempted to just go with Unity now.
It is a fair point that Open Source means you can't fix the bugs, but that's missing the actual point. Making the Quake engine Open Source wasn't just done to allow individual game developers to fix bugs, it was done so that game developers could use it, not just for free as in beer, but under an Open licence. And that other people could extend the engines, as indeed happened.
If he wants to use Unity because that's the best way to make a game, that's fine, but otherwise he seems to have an axe to grind against Open Source.
Using commercial engines, especially under a free (as in beer) licence, doesn't mean the engines are dependable or the authors "committed enough". Bugs don't magically get fixed just because it's Unity. Indeed, if you want support from Unity, you have to pay for it (
https://store.unity3d.com/products/support ). Otherwise AFAICT you're left with posting on forums. Even for paid support, support doesn't mean bugs get fixed - there may be a lack of resources, and developers are working on high priority issues, or some bugs may be really hard issues.
He says: "My fear is that a nasty bug pops up when the game ships (or during testing), and the engine coder is not motivated to fix it at that time. " - what on earth makes him think that Unity is going to fix his bugs, especially if he's using the free licence?
He's also made a more recent post, "Unity sale rumour". He dismisses the advantage of Open Source by saying "You don’t have full control over an open source engine unless you either are an experienced C/C++ programmer or can afford to hire one / are successful at recruiting one. "
Well, some people are experienced C/C++ programmers - obviously less experienced people are better off with game creation tools - but that's missing the point. The advantage of Open Source is not that you personally have to develop it, but that someone can, and it isn't lost if the company goes bust or decides not to produce it anymore.
When Nokia announced the switch from Symbian to WP, there was a question over Qt, which was then owned by Nokia due to its use for Symbian development, but Qt is also a widely used toolkit elsewhere. As it happened, Nokia sold Qt to an independent company to develop, but no one was really concerned - if Qt had have been ditched/or dropped, the source was available for forking.
And does Qt being Open Source mean I don't get support? AFAICT I get the same level of support as I would get from a free Unity licence.
His argument of a different mindset - aside from sounding rather insulting - is odd given that many Open Source programmers also work as commercial programmers. It also makes no sense for products that are produced by companies but released as Open Source (Qt, Android, or indeed the Quake engine that he ditched). More generally he seems to be arguing against a straw man (who's saying Open Source is perfect, etc?.
What about this author's mindset? If he's an indie, does also have a "lack of discipline and commitment"? Or did that magically get fixed now that he's no longer making an Open Source game?
The "open source games have never taken off" is a related but separate issue - are we talking about open source games, or engines? The state of available open source engines may be one reason for fewer open source games, but other reasons will be that it's harder to make money, as people have discussed in this thread. This isn't an issue of commercial companies versus hobbyists (as the blog author portrays it) - a lot of successful Open Source software has come from commercial support (Android, Firefox, Ubuntu, Qt), whilst a large amount of hobbyists don't release as Open Source. I'd argue a reason for lack of Open Source games is because it's not something that commercial companies seem to support, other than for old engines. Which is odd - surely the possibility of "open source code + proprietary assets" makes it still possible to make money, compared to non-game software where you have to make money through other means.