https://www.tomshardware.com/3d-printing/josef-prusa-warns-c...
The situation is interesting and kind of a grey area. The way they structured the network code as a plugin that downloads after first run is obviously to avoid violating the AGPL license, but if you don’t install it, large parts of the slicer are inaccessible. So it’s not at all like a normal plugin.
Edit: a more direct source. https://x.com/josefprusa/status/2054602354851254330
For example the Nvidia driver gets to ignore the Linux kernel license because even though it links with the kernel, when considered as a complete package it's not a derivative work of the kernel. It is its own product that can be plugged into various kernels such as Windows and Linux, and the small adapter layer for each kernel doesn't change that.
Some German court even once interpreted GPLv2 to prohibit tivoization.
By a common sense view it is not a plugin at all, it’s part of the app that they have structured in a weird way to try to avoid the obvious license violation.
Of course, IANAL and just a random passerby with a SUPER rough understanding.
What you're describing is probably a gray area, the closest example I can think of is the Wordpress plugin ecosystem (GPLv2+).