@thomas A Reed
Interesting read and this has been quite an interesting experience generally. In the end it does appear not particularly malicious.
I am sure that I never actually selected a link to download the codec. If you google whitesmoke.com you will find references to something very similar on Windows going back some time. It also appears that the download.dmg file may be downloaded when downloading from a site such as Frostwire or Pirate bay. Whereas it used to be possible to inspect, and select from, the contents of a torrent, Pirate Bay now uses 'Magnet links'. which do not enable this. Therefore it is not possible to see what will be downloaded before starting the download. It is therefore quite possible that malware such as this could be included in the download. Checking in detail the contents of the download folder could minimse this risk. NOTE THAT I AM IN NO WAY ENDORSING THE USE OF SUCH SITES!
Whitesmoke.com sell an application for "World-Leading English Writing Software"
available for Mac windows and iPhone. It includes translation and the website looks very similar to the tranlation screen shot in your write-up. The opinions expressed on this software are either 'I'ts wonderful' or 'it's a rip-off POS'. So I am wondering if this whole thing is some ruse to get people to the Whitesmoke website to buy the software???