Can I include this text editor for Google Docs to my project?
https://github.com/benjamn/kix-standalone
or this is illegal?
I suspect that this person just steal the code. If this legal how can I send the data using POST to PHP? The HTML code does not have a textarea to send it, and I couldn't find a way to send the data.
I think it's illegal because this code is not provided by Google. One reason is that it is heavily based on server-side components see this
https://groups.google.com/forum/?fromgroups=#!topic/closure-library-discuss/SeZdenR-2vA
and the link you provided contains the obfuscated code and you will have no support if you use it.
hope this help