Hi! Yes the software is fully libre FOSS I believe that nonfree (free as in freedom) clients for services like lemmy, mastodon, etc go against the very principle that the services stand for. The source is hosted on gitlab. You can find the link to contribute on the sidebar as well as here. At the moment there are no plans to support Kbin as I want to get lemmy working fully before moving on to other services. Depending on how hard it is to implement it could be on the path forward.