It is my understanding that the open enrollment period is for all individual plans whether one acquires insurance through an exchange or directly from the insurance company. The states get to decide how insurance is sold. In some states you can buy directly from the insurance company and they will process the subsidy for you if you are eligible. Of course, that is if they ever get it to work..
Since, next year, the Obamacare open enrollment period will be the same as Social Security (10/15 - 12/7) can you imagine the cluster fudge if the private insurers are thrown in too? Seems to me that the well to do (no subsidy) healthy folks will opt for an off exchange policy. This would seem to be a conflict of interest for insurers who sell individual products on and off of the exchange. DC is attempting to avoid any competition.
As for insurance bought outside of the exchange AFAIK ACA law states that only "Silver Level" policies bought through "STATE operated" exchanges is eligible for a federal subsidy.