Technically Badspot owns all the rights, I believe, even still, no one copyrights their add-ons, obviously.
I think he only owns the rights to stuff you make in-game (as in, models and builds) or possibly stuff that you publish on the forums. Besides, it's illegal (as in, it doesn't have any effect) to give away your copyrights on something in certain countries, like Sweden for example.
Also, copyright is completely automatic and you DON'T have to do something yourself. Also, AFAIK, it defaults to ARR (All Rights Reserved).
This isn't just drama, this is legal stuff.
To my knowledge, all add-ons are under the GNU license, which means that they don't really have a sole copyright holder but it's still illegal to sell it.
Nope.
First of all, I've never ever even saw a blockland add-on under a specific license, except for RTB (which is under the CC-BY-NC-ND UK 2.0 license).
Secondly, it IS legal to sell GPL-licensed stuff, even without permission from the copyright holder, as long as you distribute the source code too (which is not a concern for interpreted languages like TS). That is even officially encouraged by GNU.