Sailfish OS is already installable on ARM boards and Android devices.
You just need Mer hardware adaptation running, then install packages pulled from Sailfish SDK.

But you need to remember that like in case of Maemo, free OS does not mean that all the needed apps, plugins and codecs are free.
And pure OS without apps is good for one thing only - app development.
So yes - it's nothing wrong with Jolla allowing Sailfish OS to be installable on many platforms - it means more apps only.
On the other side, their business is safe as all the really interesting parts of Jolla phone are most probably their IP - a model we know working well in Maemo.