Nah, they haven't open sourced anything: https://github.com/rheinmetall. They just published the documentation. Really weird, what's the point?

They've got the IDL files as well for the APIs, but you can't use them without their libs:

> The data model is defined using a custom format .rmodel based on the ddkit > framework (rmodel-api).

> Please note that the .rmodel data model is for documentation purposes only and > does not reflect the actual interface used on the communication layer. Network > communication is only possible through the provided libraries.