At the time yaml-cpp 0.6 was released several packages still needed the 0.3 API so the yaml-cpp03 package was created.
Currently no package requires the library on F28 through Rawhide and it has a couple of CVE's attached to it that will not get fixed.
My intention since there are no dependencies in Fedora is to retire it immediately.
I have not yet evaluated EPEL...
Thanks,
Richard