And for the ajax call :
www.limesurvey.org/manual/NewDirectRequest
is a solution for managing API key inside LimeSurvey GUI.
Already made usage of arcgis API for such situation.
Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member. -
Professional support
-
Plugins, theme and development
. I don't answer to private message.
You might can hire DenisChenu to write a plugin for that. Keep in mind if the PHP URL gets known to others you might end up getting your API calls abused by others.