Is there a workaround for adding a graphical realtime statistic / Chart to show the online clients per hour für the last seven days on my website? Google was not very helpful.
You could record the statistics server-side and have it build and cache an http response in the data format you need; html, xml, json, etc.
C# can be used to host a simple Http Listener to serve these requests and it can even be used to generate the graphs (there are some native WinForms features to help with this), then it would be a case of simply serving the image as the Http response
If you have a shard listed with us here at ServUO then you can check your shard statistics on the graphs page. In the near future you will be able to export those statistics with our api and use them on your own website much in the same way you can grab json or xml current statistics.