I tried to flash it both after deleting my keyboard from system and with leaving the keyboard there thinking that maybe it was a skin and not a full keyboard. It will begin the install and then I get the message "installation aborted." I am using rzr recovery.
I got it to work and I thought I would post up how in case someone with rzr ever comes along and wants to use one of these. Now the only one I tested was the all black one so I am not sure about the others.
When you mentioned that it worked with cwm I remembered reading somewhere along the way that there are older update binaries (I think thats the correct term) that will still work with cwm but do not work with rzr.
All I did to get the keyboard to work with rzr was: using 7zip I extracted the latinme.apk from the black keyboard and dropped it into a gb keyboard update.zip I have used many times, since it has always worked for me I knew it had compatible update binaries. I then deleted my latinme from system and flashed my newly created keyboard update.zip like you normally would. Boom!! Next thing you know I am typing away on an all black keyboard.
Hope this helps and the keyboard looks great!!