But isn't web browser currently is a de-facto cross platform UI toolkit for displaying web pages it is just that we managed to make web pages look and behave more like apps.

So it is definitely possible to make a framework/toolkit although if you look at development history of browsers how many years it took them to get where they are and Opera throwing in the towel and switching to Blink.

Only question is, if they do such a toolkit what is there remaining for OS vendors to do? Kernels? Users will just choose faster one.

The browser is a cross platform UI, yes.

But is it on-par with native offerings? Where are the standardized components? How many years did it take to get a simple grid layout present in Tk back in 1991? Where's the fool-proof GUI editor? How long did it take for it to have a date input?

The web had to fight its way to where it is now. And that's why it has so many scars (besides the self-inflicted DOM and Javascript before strict mode and ECMAScript 5).

Regarding the OS vendors, well, yes, kernels, tools, basic apps. Also not all applications are graphical.

Native offerings kinda suck too I don't know any standardized one. Swing, QT, GTK all look different depending on the OS.

Before web stack there was Flash it had hardware access but it was insecure, now web tech going the same way with web assembly and webgl.

"Swing, QT, GTK all look different depending on the OS."

They're supposed to. They're fitting in with the OS's native look and feel. And that's a GOOD THING.

It took decades of development and an immense amount of resources - the current web engine we all use is the work of dozens of developers from KDE, Apple and Google. If we could've got those all to collaborate on a native UI toolkit you could probably have got something equally good, but such a joint Apple-Google project would probably have been politically impossible at both companies.

Exactly, and building a UI framework as powerful as the web tech is very hard.

Sorry if I go OT, but I wouldn't know where else to ask this since the question comes from the article you linked.

So, by the logic of making your complements a commodity, what is FogCreek trying to make a commodity of with Glitch? Are they trying to make "building apps" (and thus "getting into programming") a commodity so they get more users to StackOverflow?

Also, does anyone have any good material to suggest on this topic? I'd like to learn more about it and learn how to be able to recognize the things for what they are: complements or products.

Well, as I think Joel says in the article, you want some sort of Econ 101 textbook. Regarding FogCreek, you need to be aware of the whole picture: when Joel's talking about strategy, especially at that level, he's talking about big companies. Fog Creek doesn't have the kind of pull necessary to really care about complements or substitutes. Their strategy is probably: "fill whichever niche we deem free" :)

Oh yeah, I was thinking of something more specific, but I'll look into that too.

Well but then there's a big missed opportunity there, isn't it? I mean, it sounds like a principle like that would apply to most scenarios, unless you are too small to even think of making an impact on your complements markets with your financial power. In that case, sure.