Ham radio is about experimentation and learning, but almost all radios used by Amateurs today are closed source and proprietary. The protocols themselves are usually more accessible, but require proprietary bits to actually implement, such as the voice encoding software.
All current VHF+ digital radio protocols (D-STAR, DMR, Yaesu System Fusion, P25, ...) use some form of AMBE voice codec - which is patent encumbered and expensive to license, and certainly not available to the average ham. At the time these protocols were designed, AMBE was the only choice, but luckily, there is an excellent modern vocoder that is fully open - Codec2, by David Rowe.
There's been a lot of work on making radios like this more accessible and more open, like all the work on OpenGD77, and MD380tools, but without open software from the OEM, this is a hard slog, constantly working just to stay in place. Even with fully open replacement firmware projects like OpenGD77, closed hardware means an incredible amount of work reverse engineering how the radio works.
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