Why so many versions of the port science/hdf?

[Stephen Montgomery-Smith]

Why are there three versions of science/hdf in the ports?

This is causing problems for me when I try to build the port 
octave-forge.  As dependencies, it calls in the octave port (which 
currently defaults to hdf5), the cgnslib port (which uses hdf5-18), and 
the opendx port (which uses hdf).  All of these ports function perfectly 
well with hdf5.18, because all the different versions of hdf conflict 
with each other.

If we could settle on using hdf5-18 throughout, that would be great.  (I 
currently maintain opendx, so that would be something I can fix.)

Are there ports that need hdf but don't build with hdf5-18?

Thanks, Stephen