E.g. I might get something like this (dumped from python, not the original JSON):
{u'phid': u'PHID-PROJ-mpdzefr4qyk2vcbpxlud', u'profileImagePHID': None, u'color': u'blue', u'name': u'Interrupt', u'slugs': [], u'members': [u'PHID-USER-boqv2doznygy3kwrkyly', u'PHID-USER-mzjfuzwqhxgtksmcqpn3'], u'dateModified': u'1455907145', u'dateCreated': u'1455907145', u'id': u'1795', u'icon': u'milestone'}
https://phabricator.wikimedia.org/project/manage/1795/ says this is a subproject of Phlogiston