That's "just" a makefile, which should be rather simple. The true challenge, apart from what was already mentioned as the probably incompatible API, the interface file itself, IB.nib, which is a serialization of the interface. Reading the file on latest macOS is still possible, but for deserialization it can't find some of the classes (e.g. StreamTable).
If you want to dig deeper, try the NeXTStep 3.3 developer disc: https://archive.org/details/nextstep3-3dev