If you read the article, it is indeed full Linux because the 4004 is running a MIPS emulator that provides the necessary memory management features. Pretty much all of the “run Linux on some old chip incapable of running Linux” projects achieve it via emulating a more featured architecture that Linux supports, not by somehow compiling Linux to natively run on a 4 bit, MMU-less architecture.
Mozilla sold out a long time ago, they are nothing like they used to be. Everyone should be ditching Firefox for forks if possible. Yes, Firefox is still miles ahead of anything Chromium-based but we can’t trust Mozilla to not screw over their users anymore (and it’s been apparent for YEARS…Pocket, “Sponsored” shortcuts and links, Mozilla VPN popup ads, this behavior is hardly new). What can we trust? Firefox forks with the bullshit stripped out, mostly. I’ve been using LibreWolf for several years on my Linux, Windows, and MacOS systems now. I originally switched because of the Mozilla VPN popups but at the time, complaining about those popups was met with a bunch of Mozilla apologists going “it’s not that bad” “they’re a big company and they need their precious monies”…no. That was ADVERTISING front and center, and it was in Firefox years ago. So was Pocket. So was having Amazon links auto-filled on the new tab shortcuts. Go to something that isn’t run by money. Go to a community-maintained and sanitized fork.