There’s everything there to build an RPM, however it depends on harbour-themepacksupport so we would need the source for that as well.
I have successfully built (but not installed/tested) an RPM from the linked source tarball. It does compile on the 184.108.40.206 SDK, but fails on 220.127.116.11. So there is some porting effort needed to bring it up to current versions.
On a personal note, the linked source is GPL so everyone is free to fork/modify/distribute. OTOH I think the original developer’s wishes should be respected or at least considered when resurrecting such apps from e.g. archive.org.