Morse Classic is a Morse code training program for aspiring radio hams. It can generate random tests or simulated QSOs resembling those used in the ARRL test (a QSO generator is included). There are a plethora of options for varying the training method. In one of the simpler modes, this program will take text from standard input and render it as Morse code beeps.
Salut is a small program that performs calculations on simple networks around two-port devices (like transistors) characterized by s-parameters, at radio frequencies (RF). It has the ability to model components in series with a two-port block, like an inductance from the common lead to ground. Salut is also not restricted to the usual common emitter or common source configuration even though many semiconductor manufacturers only provide s-parameters for this case.
Open5066 is an implementation of the NATO NC3A STANAG 5066 protocol stack for HF radio communications. It aims to implement all of SIS (Annex A), DTS (Annex C), and some of the application layer (Annex F) functionality such as HMTP. The concrete embodiment of Open5066 is the s5066d daemon.