The port 4567 is away in use, possibly do to nodebb already running. Google "how to kill process on port" and you should be able to kill whatever process is already running.
I've searched the forum but haven't find an answer to my question.
Is it possible to host NodeBB on my server. What's the price of the software in that case?
Yes! Most members use a self-hosted solution instead of one of the plans provided by NodeBB, so far as I know.
You can get started here: https://nodebb.readthedocs.io/en/latest/ (Documentation).
And here is the source code: https://github.com/NodeBB/NodeBB/
If you want to install it: do not use the development branch but 1.x.x, or one of the releases.
Thanks for your quick answer.
I have sold my forum recently that was hosted on IPB. I was so frustrated with it and it is becoming worse with each update... Since I plan to start a new forum I am currently testing Flarum but its development is pretty slow. The only advantage over Discourse is that it can be installed on CentOS 6. If I remember correctly Discourse requirement is CentOS 7..
Today I have found out about nodeBB and those three forums "feel" very similar (Discourse, NodeBB and Flarum), although at first NodeBB seems more advanced.
I will try it for sure..
NodeBB is the way to go. I use CoreOS with my own Docker packages (NodeBB + MongoDB)