Signal Desktop is an open-source messaging app that uses the Signal protocol to secure your communications. It is developed by the Signal Foundation and is available for Windows, macOS, and Linux.
You can find the source code for Signal Desktop on GitHub at the following link:
https://github.com/signalapp/Signal-Desktop
There, you can access the latest version of the code and view the development history of the project. You can also report issues or contribute to the project by creating pull requests.