M17 Protocol implementations for Internet (non-radio) use:
mvoice is an M17 Protocol digital voice client, written for Linux.
DroidStar is a multi-platform, multi-protocol digital voice client that includes M17 Protocol support.
MMDVM_CM Doug AD8DP's fork of the MMDVM cross-mode tools includes many M17 transcoding options.
DVSwitch includes M17 Protocol support as an experimental feature.