Hi Bob :-)
The funds get locked in a multi-sig. If Alice would 'refuse' to pay Bob she wouldn't gain any advantage since she can't get the funds out of the 2-of-2 multisig.
Well, I've signed the money over to her, and I signed it with my key. Now if she signs it and broadcasts it, 2-of-2 multisig is unlocked.
If an malicious actor 'breakes the rules', an earlier state is going to be published, which depending on the case, can lead to the attacker losing all of his coins.
If an earlier state could be published by me, can't I then defraud an honest Alice and publish the earlier state after she sends money to Bob? I thought the clever idea of channels was that only the second person can actually finish the multisignature and so he's the only one that can broadcast and publish the final state, the latest with the most funds signed over to him.
I'll take a look, thank you.