Well, my stupidity is showing.
I thought passive skills were just skills that didn't need to be activated by a click, and active skills were skills such as heal, which normally require quanta and always require...erm...activation.
Perhaps the best would be a split among active, passive, and innate.
Active abilities are those that have a quanta cost associated with it.
Passive abilities are just there, but, like active abilities, can be subject to removal.
Innate abilities are part of the card, and are not removable by normal means.
All three can coexist, I believe. For instance, I can mutate a devourer with mutation, then grant it momentum.
Of course, I say this because that is pretty much what my misunderstanding was. At the very least, I am straightened out now.