Subject: Re: The gag order and testifying?
So then he's not really gagged at all when testifying, though with an ability to still threaten witnesses and jurors, and apparently without any penalty other than a reprimand and cease and desist by the judge? What's the worst penalty the judge could impose?

He could imprison him. Find him in contempt and impose a criminal sentence. Same as with the gag order. If Trump elects to take the stand, the judge will almost certainly instruct the witness on how is to comport himself while testifying - and if Trump disregards those instructions, he can be found in contempt and sent off to jail.