Quick work around was to click the PTT button on the FreeDV screen and then key the microphone on the FT-857 to put the radio into transmit mode. This worked but was not ideal to say the least.
With a little help from David, W5CTW I acquired the Hamlib-Yeasu dll file from Hamlib and placed it in the FreeDV Binary folder.
The next time I started the FreeDV software there was a whole list of Yeasu radios to pick from. I simply picked the FT-857, set the COM port to the one that my CAT cable was using and clicked on apply. Now I can simply click on the PTT button in the FreeDV screen and the FT-857 goes into and out of transmit mode without me having to key the radio's microphone.
Controlling a transceiver from a computer may still be a bit confusing but it certainly opens the door for a lot of potential neat stuff. Like it or not, I believe that this is the direction of the future, computer control of our radios and other devices.
Anyway, take a look at the Hamlib website. There are some applications listed there that might be interesting to download and try out.