I recently set one of these up for my daughter, and there is indeed no way to use the display without a Roku account, and that does require a credit card, and sneakily tries to get you to sign up for trials, as the article mentions. It took a lot of effort for me to make sure my (3 year old) couldn't order HBO, etc.
Had I known that, I woudln't have bought it. It's easy to envision a future where Roku is out of business and this tv can't be activated again if needs be.