Yes the checking not false rather than equal to true option didn't seem to be working either so either comment out or probably just remove the condition e.g.
//if (iframe.allowfullscreen != false) { --delete this line
html += " allowfullscreen";
//} - and delete this line
Then possibly clear cache/offline files before refreshing and trying again.
HTH
Ron
Well, I cannot think of a good reason not to allow the control to be there: it's up to the user whether or not they use it which is in-keeping with our 'put the user in control' principle; it's good on tablets / phones and it's just generally good accessibility-wise. I don't know whether youtube users can choose to disable this when a movie is published, but ultimately surely it's up to the end-user whether they use it or not?
I've commited a change, and removed the condition.