Clinton explained the politics that were going on at the time around gay rights issues, and it confirms what I have suspected, not only on this issue, but others as well: if Clinton did not advance a progressive agenda as much as some liberals would have liked (like, say, Ralph Nader), that was largely because he had to deal with a Republican Congress. If Clinton didn't make liberals happy, they should have been thankful that he was a firewall against much worse legislation being passed.
On DOMA, he makes a point I was not aware of: there was a real danger that Congress - both houses of which were, at the time, controlled by Republicans - was going to send a constitutional amendment to the states banning gay marriage. DOMA may be bad, but a constitutional amendment would have been infinitely worse, because it would have made gay marriage impossible in any state. So on gay marriage, Clinton may look like a bad guy for signing DOMA, but he was just making the best of a bad situation. Because if the Congress had sent that amendment to the states, it would have passed very quickly.