Can I file somewhere else once I'm registered

[AnthonyC]

Yes, you can.  You are free to file elsewhere until you actually hit the "Transmit Return" button and your return gets accepted by the IRS.  The only caveat to being registered in the program is that you won't be able to clear out your return using the Clear and Start Over feature.  But, this won't have any effect on you being able to file elsewhere.  Your return will be automatically cleared out at the end of the tax season.