Nearly two years ago you merged a pull request which added some support for more modern CMake.
A step toward the right direction I think, but unfortunately the CMake code now includes variables like YAML_CPP_LIBRARIES which leads to spaghetti code somehow...

It would be beneficial if you would export your targets instead, this is considered best practice, is there any good reason why you don't do it yet? If not, I can try to come up with a patch.

Have a look at https://pabloariasal.github.io/2018/02/19/its-time-to-do-cmake-right/#good-boys-export-their-targets

If ready, one could import the library and all necessary includes, flags,... via

find_package(yaml-cpp 0.6.0 REQUIRED)

target_link_libraries(${PROJECT_NAME}
    PRIVATE
        yaml-cpp::yaml-cpp
)