It's not posting anything. It's using the post management interface to read posts. Apparently LJ has some kind of strict throttling that Dreamwidth doesn't have. Or perhaps it's the difference between paid and non-paid accounts??

The script output mentions items, like "L-1018", "L-1019", etc. Each of those is either an entry or a change to an entry. When you run it again, do those L numbers change? Or does it always mention the same set?