The article addresses this. The open source implementations are not complete so there are compliant files they cannot render. Also they have rendering bugs which mean some content does not render properly, and worse some files they generate render fine now, but are not compliant and if the code is fixed those portions of the files may stop rendering correctly. Some of these issues only manifest at particular zoom levels, so you are never be sure what you are seeing is correct. This us all part of the problem with the spec being so complex.

Software rots man. It can be really hard to run some open source software from the 80s and 90s. This is actually one of the big arguments for Open Source: Access to the software is way less interesting than the support/community/ecosystem around it; there's no reason not to open source your software and not doing it actually harms the users.

Yeah, Pixar literally had to spin up VMs of their old software stack when they had to remaster the Toy Story films because it was less work than getting it running again on their current stack

Actually, it seems to me VMs are an ideal way to preserve things like that. Perhaps it should be standard procedure for the archivists of such big films to build and preserve a fully functioning, self-sufficient rendering environment in the form of a virtual machine.

Until we switch to another architecture. It's pretty likely the x86 architecture will be gone in a few decades. Rebuilding VM software to run on new hardware is probably harder than fixing bugs in a JPEG decoder.

But you only have to rebuild the VM software once to get access to all kinds of software that ran on that architecture.

A few decades? The IBM System/360 architecture is still being shipped, and that first shipped in 1965!

Nobody ships a PDP11 or VAX anymore. 6809? 6502? I think even the one ubiquitous 8080 isn't being produced anymore. And when IBM falls, System/360 will also be gone. There will be a transition period in which everybody scrambles to convert their systems, but after that it's EOL.

I know someone who got hired recently to get PDP11 software running in an emulator to control an industrial process.

I expect that to happen to /360 as well (there's more than one emulator; there's even support for the old consoles), but the hardware will be gone. And --in case of the JPEG2000-- once x86 is gone, it'll be an old decoder running on an old, unsupported OS running on unmaintained VM software running on a hardware emulator (which will also have a limited support). Not a great outlook.

Dude, that's why we use Virtual Machines. We will run them thru QEMU or another multi-architecture solution.