If anyone is interested in using Single Transferable Vote for unofficial uses, I recently wrote an implementation in Elixir and wrapped it in a small JSON API. It is a toy in its current state (it uses cookies to see if people have voted and the link to close an election can be somewhat easily found even if you are not the creator of the election) but we use it around or office for a few things and I would be interested in continuing work on it if anybody would like to jump in. I have an instance of this running on my site; ping me if you'd like to try it.
STV Algorithm: https://github.com/carrigan/elixir-stv Phoenix API: https://github.com/carrigan/vote-service