EchoLink
From Wildsong
EchoLink is a closed source Windows program that allows communication over 2 meter radio by connecting radios and the Internet.
Why is there no source code for the clunky old Windows program?
Linux
SvxLink
https://github.com/sm0svx/svxlink
SvxLink is a project that develops software targeting the ham radio community. It started out as an EchoLink application for Linux back in 2003 but has now evolved to be something much more advanced.
There is an EchoLib library
Hardware
I think a couple of my rigs contain the hardware.