Hello
REST API is available, documentation is in Apiary.
Also a JavaScript API is available, you can have a look at JSPs files within the knowagesdk project:
https://github.com/KnowageLabs/Knowage-Server/tree/master/knowagesdk/src/main/webapp
You can find documentation within the example JSP files theirselves.
Hope this helps
Regards
link that you mentioned above is not found.
(https://github.com/KnowageLabs/Knowage-Server/tree/master/knowagesdk/WebContent)