In your other comment you laid out potential uses for a "unlocked" ipad
web browser
IoT control panel
video conferencing
photo frame
e-reader
kiosk
The bottom 5 don't really need updates and if Android tablets are anything to go by (looking at you Nexus 10) arguably will work better running on top Apple software instead of whatever half baked garbage gets dumped out of the major distros or "custom rom" makers.
For web browsing, a nine year old tablet will arguably be slow as molasses for the content that would be on the web nine years from now. We have seen this with using old desktop computers to browse the web.
Your argument is pretty weak. There is a whole lot of work to make this happen among not only Apple but the OSS community for almost no gain. The community's time time would be better spent getting fundamentals of Linux Desktop working well so that maybe one day in our lives it really will be the Year of the Linux Desktop™.