Indeed, there is no free trial for this application. On the official website it's specified about the Download, but it leads to the purchase page from where it can be acquired for Windows and Mac operating systems.
I've checked all the sections on the website, but there isn't anything about the possibility to download a trial version.
You can contact the developers to ask them about the trial, maybe they give I to certain customers. Use the following link to reach them: http://www.hemingwayapp.com/help.html