This is a native native plugin for Unity 3D engine to support development of client applications for Vircadia Open Source Metaverse Platform. The project itself serves as an example, with the SDK set up as an embedded plugin.
You'll need to build Vircadia client library that provided a native API for communication with the server side. Clone the main Vircadia repo and follow the instructions for you platform. After the cmake configuration step, instead of building usual components, you can just build the client library by following the instructions in libraries/vircadia-client directory. Once build copy the client library binary from build/libraries/vircadia-client to Packages/com.vircadia.unitysdk/Runtime/Plugins/ in this project. You might need to copy some dependencies as well, to identify those you can use ldd or objdump -T or an equivalent. Then you should be able to open the project in unity editor, open and run the TestScene and run the unit test in Runtime section of the Test Runner, available under Window->General->Test Runner.
The SDK is documentation using standard C# XML formatting. docs/Doxyfile is a basic configuration for generating documentation with doxygen:
Running doxygen ./docs/Doxyfile in the root of the project will generate html and latex documentation in the docs folder.
The native client libraries will need to be built for each supported platform, and copied over to the plugin directory along with all necessary dependencies. The target OS and architecture will need to be configured in the editor for each library file. With that it's sufficient to just create and distribute a zip/tar archive of the contents of Packages/com.vircadia.unitysdk directory. The archive can be imported directly though Unity Package manager.
This process can be automated once the client library takes shape and it's dependencies on any given platform stabilize