It is clear that this site is maintained by James O'Donnell, a professor at University of Pennsylvania. His address and phone number are easily available giving authority to this site as well as his extensive professional qualifications as an expert and published author on Augustine. The site contains many illustrations and texts as well as translations. The copyright status of the illustrations is questionable, however all would be originally published prior to 1923 indicating that they may be free from violation. The texts included are either in the original, and therefore ancient, language or in translation.
All translations indicate the translator.
O'Donnell's own work is all copyrighted clearly. With regard to accuracy, the web page seems to be well proofread and of scholarly standards. Everything is either credited to the O'Donnell or another source in such a way that would be simple to verify the information provided. This site is clearly designed to complement the scholarship of the author. That it is located on the UPenn site indicates at least some endorsement by the university.