For the record, this was never really true. The backend of dmd (the "main" D compiler) was unfortunately not under the same licence as the rest of the compiler, but the code has always been available. The GNU and LLVM backends are both fully open source and are faster anyway.
[And yes, I realise this comment is a perfect example of those weeds.]
¹ Although, I appreciate far less than either you, or especially WalterBright, have.
A better way to clarify it would be:
There are three D compilers available. Two of them have always been fully open source. Parts of one were originally source available rather than open source, but that one is now 100% open source as well. The website failed to communicate this information properly at the time the author first tried D.
The D website had, shall we say, uneven quality of communication back in the old days.
However, I do like your full and complete answer. It acknowledges the old situation and completely nullifies it. I'll steal your second paragraph for when coffee time returns to normal ;)
The term the author used ("open source") has a specific meaning. Merely being able to see the source code is not sufficient.
Given my role at the foundation I need more data on this so I'm not being facetious
The compiler page has a lot more details than I remember [0]. It says: For beginners you should use dmd, but the next sentence says that LDC/GDC produce substantially faster binaries. So why would I ever choose dmd? What are the trade offs? Compile time? What is substantial? And then when you scroll down it doesn't say what version of the D language spec is supported by each compiler, imagine getting started with LDC and then it only supports D 2.02, when dmd is up to D 2.12 or something.
I guess for me there were a lot of questions to getting started.
There was a compiler called DLI that even used the front end code and wrote a new backend that used nasm. I remember porting that to BeOS because none of the other opensource back ends were easily portable at the time.
So my understanding is there’s a COM APIfor automating Office applications that seems to launch a headless version of the application, some sort of newer JavaScript API for interacting with Office365 applications, and if I recall correctly, some sort of COM API for actually extending the application which I assume is what the D-wrapper in this article is using.
[0] https://docs.microsoft.com/en-us/office/client-developer/exc...
If anyone's interested in it from a Dot Net perspective, ExcelDNA [0] was excellent when I used it a few years ago.
COM however does not allow you to create your own user defined functions in excel, so for that you need to create an xll (for instance via Excel-DNA).
I am less familiar with the javascript API but I understand it is newer, and meant to create components for office 365, it does not offer the full access to the office API.
The two historical programmatic interfaces to Office (that I'm familiar with):
VBA[1] - They have a pretty extensive VBA object model for the various Office programs, and is used for macros (either by auto-generated code when you "Record Macro" or manually developed code). The code lives within the Office file and follows it around, allowing it to be fairly portable since it doesn't require anything external to the file (unless you're calling out externally or relying on things like ODBC drivers).
You can also package up VBA into add-ins as well.
COM - There's an interopp assembly[2] that exposes a COM-based object model. This is the object model being used here (via Excel-DNA[3]), and the one hooked into by Visual Studio Tools for Office[4].
The biggest issue with both of these is cross-platform support – historically add-ins have been Windows only. COM isn't supported anywhere else, and VBA is only supported on Mac (not mobile). And the Mac VBA model isn't nearly as robust as the Windows version and has several caveats[5].
Enter Javascript, which is a relatively new option and what they're pushing hard get people onto. They've started developing an object model to expose the various Office apps via Javascript[6]. When you develop an add-in using this[7], the add-in is actually a webapp running in a sandboxed browser, with transparently handled interop between the add-in sandbox and the Office app. So all of the actual add-in development is HTML, CSS, and Javascript based.
The primary benefit of the Javascript option is that they're portable between the various platforms ([7] mentions Windows, Mac, Web-based, and the iPad. Not sure about Android/iPhone). But you get a lot of secondary benefits as well, such as the ability to have your add-in resources loaded from a remote website, ensuring things like the user always loading the latest version.
They've also slowly been making inroads in expanding the usage of Javascript - Office Scripts[8] is a preview feature they have right now, that effectively allows you to record macros in Excel for the web, which generate Javascript-based code rather than VBA code. You can also create user defined functions[9] in Javascript that can be mixed with normal functions within cells.
I (unfortunately) have to use Excel for many end-user deliverables, and have tinkered around with the Javascript options to make a few quality-of-life utilities for myself and others on my team. It's super handy for plugging into online services, and for being portable. I have one or two utilities for external teams that they access via Excel Online but I don't give them the file, and for others on the team we have several in circulation the Javascript-based stuff all "just works" in these contexts.
A major caveat of the Javascript stuff is that it all runs in sandboxed contexts and can primarily only interface between the Office host application and external services. COM and VBA-based add-ins don't have this constraint, and interact with other local resources beyond the host application itself.
On the plus side for the JavaScript option – in addition to being cross-platform, they're also not nearly as locked down in corporate environments because of their reduced security threat. But that limitation also means that it's unusable for solutions like this D in Excel add-in, which couldn't execute in that browser context and require the COM interop capabilities.
[1] https://docs.microsoft.com/en-us/office/vba/library-referenc...
[2] https://docs.microsoft.com/en-us/visualstudio/vsto/office-pr...
[4] https://docs.microsoft.com/en-us/visualstudio/vsto/create-vs...
[5] https://docs.microsoft.com/en-us/office/vba/api/overview/off...
[6] https://docs.microsoft.com/en-us/javascript/api/overview?vie...
[7] https://docs.microsoft.com/en-us/office/dev/add-ins/excel/ex...
[8] https://docs.microsoft.com/en-us/office/dev/scripts/resource...
[8] https://docs.microsoft.com/en-us/office/dev/add-ins/excel/ex...
[9] https://docs.microsoft.com/en-us/sharepoint/dev/general-deve...
...true for a programmer. Office worker using primarily Excel who the IT team is trying to protect against threats...not so much.
I can't even change the wallpaper...
https://9to5google.com/2020/06/10/android-phone-wallpaper-so...
Not saying it’s likely, just saying you never really know where a technical or security issue may come from.