We need to catch up on this because the people who know how to use language for propagandizing don't have the best intentions in mind.
But using the original term is not enough. We need to combat their word-twisting by upping them. We need a way to convey "their way of installing stuff by default is inferior and an attack on liberty".
Something like:
- direct install: installing as we always did
- caged install: installing through a locked store.
Maybe somebody better at marketing can find a good way to do this. In fact, we should have a whole site and community to organize together and shift the narrative on all nerdy things: formats, open web, DRM, patents, etc.
We have been weak on these points for so long because we care much more about solving tech problems than selling them. But openness is being eaten away under our noses. Has been for years.
That said, I do think words matter and I always point out that the reason these systems are locked down is because of Digital Restrictions Management. I also refuse to buy anything from Sony because they changed their mind about letting me install linux on the PS3.
I just think side loading is good way to describe installing custom software on a non-general purpose computer, and that not every computer needs to be general purpose. It's significantly better than the previous terms of hacking, cheating, stealing, and voiding your warranty.
When I think of "install" I think of general purpose OSes which can install software from almost any source no questions asked, or use the native out of the box support for software installations.
The similar distinction exists with android and iOS, and is probably why the term is popular in those communities too.
If nothing else, the term sideload makes very clear on platforms with native appstores or locked down distribution channels (consoles, phones...) that the install did not come from the native channels. Installs from game discs or the xbox store are inherently different from developer mode software and using the same term "install" for both disguises this fact.