Talon is not open source as far as I know. It's freeware with Patreon early access and support. The community plugins cover a wide range of applications and are

Talon is not open source as far as I know. It's freeware with Patreon early access and support. The community plugins cover a wide range of applications and are easy to modify. I also found their Slack good for discussing accessibility options like gaze tracking. It looks like development has slowed significantly but the developer recently rewrote the core in Rust.