alt Hacker NewsWindows is an open platform for developers... if you ignore all of the security checks and Windows Defender and the stagnant platform which is about 2 decades behind everyone else, across the board, in terms of native tooling (e.g. which UI framework should I use and is it good?).
However, Windows also has many, many, walled garden things bolted onto it. You aren't distributing your own drivers without Microsoft's approval. You aren't running Microsoft Office on Wine. You aren't connecting to Active Directory without Microsoft's blessing. You aren't making group policies that work on Linux for MDM. You aren't manufacturing Windows devices, at all, unless they meet Microsoft's system requirements and mandates (e.g. a Windows icon on the keyboard). Your BIOS must follow strict rules about where the activation key is fused. Etc.
In that respect, Windows is only open from an end user perspective. In all other respects, it is closed, and it is closed tightly.
> You aren't distributing your own drivers without Microsoft's approval.
Only kernel drivers.
> You aren't connecting to Active Directory without Microsoft's blessing.
I think you're talking about EntraID. That is true enough. You can just spin up Windows Server and create a domain controller, no problem. You don't need Microsoft for domain services, though - you can use other domain controller types. (You don't get GPO and other things - that's not a 'walled garden' thing, that's a feature set which other systems don't have)
> In that respect, Windows is only open from an end user perspective. In all other respects, it is closed, and it is closed tightly.
Not so tight as you seem to think. And anyways, I was specifically referring to building windows apps - which you did not disagree with. You absolutely can pull down various free tools, build an app, package it up as a .zip or .msi and distribute it from a variety of places. The Windows app store is a walled garden, but you don't have to use it.