The latest Official Release of HDF is 4.2.13
HDF4 (also known as HDF) is a library and multi-object file format for storing and managing data between machines. There are two versions of HDF technologies that are completely different: HDF4 and HDF5. HDF4 is the first HDF format.
PLEASE NOTE that although HDF4 is still funded, new products should be developed in HDF5. See this FAQ for details.