@Aoki nodebb need node is as prerequisite.
@Aoki here is the link to nodebb docs . It will help you http://nodebb.readthedocs.io/en/latest/
Yes. Nodebb is completely free and open source . Like you I am also new to nodebb. It's good. Yet to discover it's full potential. I am using digital ocean server . I downloaded it there . If your server allow you can can upload it via FTP .
I have installed nodebb on digitalocean. Installed successrfully . But unable to get it via any url using broswer..