No, that doesn't mean that he has to 'allow' you to use it though. At least not by permission. IE, he may reserve the right to only allow you to see it, not to use it in your own worlds.
Yes the tower looks pretty good, and I bet the view from the top would be great...
Now don't get me wrong on the permission thing either. I have no idea what the true intentions are of the author. Hopefully, they will release it to the public for use elsewhere, but sometimes people want to keep things for themselves and I have to respect that.
I much prefer the way people tend to create somethign for others to enjoy and then let them have it to enjoy as they please!
Come to think of it, if everyone has the same content on every server... hrm... at some point I guess players may say to themselves "been there, done that!".
I don't encourage not releasing content to the public and keeping it private, but if you work hard on your PW and create new content well, it makes your server a little more unique. Sure there are other ways such as a multitude of area designs and a multitude of placeables setups... but having some private content may not be such a bad idea after all. But it sucks when people give screenshots of a creation they may not or will not release. Well specially when the new stuff looks awesome :_spank: