I already installed Livecode on my pc, very easy to install, easy to use, looks great

but it doesn't work, I couldn't find any other documentation on posible errors and solutions on this step, and I'm also not sure if Livecode Server is 100% free or if I have to pay something in order fot it to work, also I would like to know if I can use JSON and web services to pass data between my app and the Server.
-Long story short, I would really apreciate if someone knows where can I fin info or can tell me about:
1) is Livecode Server 100% free? can I just go to Livecode website, download it and use it?
2) what may be the reason it doesn't work when I try to run the "hello world" from command line? (assuming that Linux Apache PHP and MySQL are correctly configured)
3) when I finally install correctly Livecode Server, can I use JSON and web services to pass the data between my app and the server right away, or I would need to install a plug-in (which plug-in)?
Thanks a lot for your help, I'm really looking forward to learn Livecode, and really apreciate your help on this, as it is not available anywhere else
