Hello Baifo,and welcome.
![Salute](images/smilies/salute.gif)
ZeeWolf's mod isn't multi-player,it's single player only.
TvsT does have multi-player but it was very bugged.
Someone was working on that side of things but the guy very sadly passed away.I can't tell you the state of on-line play at the moment but Frinik is sure to know and he will be along soon.
I also have SP Pro PE and as far as I know there is no fee to play on-line.
All info you will find here though
http://www.steelbeasts.com/
As for ZeeWolf's mod,he currently is asking for 12 months subscription,for which you get all of his work during that period.