As the caster demo is the update for the full version of caster somebody would just install it over it if you would not want to use steam all the time. I would not call that protected then. But one thing is unlogical: when you use steam you get win AND mac version automatically (just depends which os you boot) but when you buy it directly then you get only one version. When you would think that steam would run on linux too then you could get all 3 variants with one buy.
No announcement yet.
It's Official: Valve Releasing Steam, Source Engine For Linux!