Since docx files are just zipped XML you could just unzip the docx file and presumably pull the author information out of an XML file. Not quite sure where it’d be stored, just looking around at it briefly leads me to suspect it’s stored as dc:creator in docProps/core.xml.
Here’s how you can open the docx file and retrieve the creator:
import zipfile, lxml.etree
# open zipfile
zf = zipfile.ZipFile('my_doc.docx')
# use lxml to parse the xml file we are interested in
doc = lxml.etree.fromstring(zf.read('docProps/core.xml'))
# retrieve creator
ns={'dc': 'http://purl.org/dc/elements/1.1/'}
creator = doc.xpath('//dc:creator', namespaces=ns)[0].text