FOSS gamedev and creative worlds

hey is it possible to host a server on a website?
like with FTP or something?
cause that would mean, that my server could be open 24/7 :D

Nope, you would need a dedicated server or at least a VPS. Your basic shared web hosts don't give you shell access, and if they do they don't allow running game servers or any long running process. Even some VPS don't allow running game servers because of their resource usage. The cheapest VPS I've seen that doesn't explicitly restrict game servers in their terms is http://wooservers.com/ I haven't used them but I'm considering it. I have a RocketVPS server but they explicitly restrict game servers.

Take a look at this guide for Minecraft, should be similar.

i read that article, but there's one thing i dont get...
do i need Linux server/Ubuntu server?
just like he did?