Yes. S-Mode won't install any app that isn't supplied through the windows store.
I would guess that it could still be a free app which requires a license after the trial period though. I'm certainly not a programmer, so I have absolutely no idea what kind of mountain or mole-hill I'm asking for.
With any hope, this may be a short-term fad with Microsoft to compete with the Chromebook ads, but all the manufacturers seem to be jumping on board since it allows them to sell sub-standard hardware with better looking specs... "all-day battery life! no viruses ever, we swear!!" :-)