After reading that thread (and others) and doing some further research, it seems to me that at this time Rhasspy seems to be by far the most feature complete and stable alternative out there right now, and also seems to be actually completely F/LOSS
I guess that depends a bit on your preference … if you are looking for a voice assistant that works with openHAB out-of-the box and is already set-up to understand a lot of smart home related commands you may also want to check out SEPIA. The current release version is still a bit limited, but further down in the thread you will find a test build of the (soon to be released) next version that understands a lot more smart home devices, rooms and actions.
If you like to train your own speech recognition though that is possible with SEPIA but more comfortable to do with Rhasspy at the moment thats true 