I have 5 computers (services) that are controlled via http-post. 3 of these services are implemented as labview webservices, 1 is labview socket (with python http-wrapper) and the last one is implemented with c# (lighttpd + cgi).
Can I use webui builder to controll all of them? Or, what is the simplest change so I can use webui builder?
There are HTTP VIs (HTTP GET/POST/etc.) available in the Web UI Builder palette that you can use to send HTTP requests for non-NI web services. There are also string manipulation and XML VIs you can use to help construct the requests and parse responses.
Here is an example that shows how to talk to non-NI web services:
Web UI Builder Product Manager
To add to Mike's answer, the only caveat is that the server needs an appropriate clientaccesspolicy.xml file at the root level (http://yourserver/clientaccesspolicy.xml), or a completely open crossdomain.xml file, for the editor and built apps to be able to communicate with it. There's a help topic which explains this in the context of LV web services, but it's true for Web UI Builder to be able to communicate with arbitrary web servers also.
Since it sounds like you control all the web servers in question, it shouldn't be too difficult to get this file in place, though.