When I try to generate PDF from a simple HTML using only the XMP data option to set the creator, the wrapper returns the following error from the prince executable:

error: bad JSON in job chunk

I debugged the JSON that the wrapper generates for the prince executable and it looks fine:

{"input":{"type":"auto","javascript":false,"xinclude":true,"styles":[],"scripts":[]},"pdf":{"embed-fonts":true,"subset-fonts":true,"force-identity-encoding":false,"compress":true,"pdf-xmp":"file:///C:/Users/twouters/AppData/Local/Temp/wbd-xmp-891176311529431943.tmp"}}

When I generate a pdf using the command line using the --pdf-xmp option it works fine, the pdf is generated and the creator is set (so the XMP file is fine).
The command line:
prince.exe --pdf-xmp file:///C:/Users/twouters/princexml/meta.tmp test.html -o test.pdf

I think there might be a problem with the prince executable parsing the JSON somehow?

Yes this is a bug we will fix shortly, sorry for the inconvenience.

This is fixed in the latest build, thanks for letting us know!

Thank you for the fast response.