Yeah I'm thinking of contributing to and taking from Cboard. Basically I want to great an interface that uses the symbols to help a kid not just interact with peers to talk to them but also say write and send a note.
Disclaimer: yes, I'm affiliated :)
I contribute to Optikey and was involved in OpenVoiceFactory in its first incarnation. Optikey is primarily QWERTY based but does supported the Communikate pagesets - more general OBF support would be a welcome PR! Coughdrop is probably a better fit for your needs, and is open source so free to self-host, though they do offer hosted plans for $.