Countless authors have contibuted to LATEX2HTML. The originating author was Nikos Drakos, and in the later versions, Ross Moore took a leading coordinating role. Please see the online manual for a proper review of all credits.
Netpbm is based on the Pbmplus package by Jef Poskanzer, first distributed in 1988 and maintained by him until 1991. But the package contains work by countless other authors, added since Jef's original work. In fact, the name is derived from the fact that the work was contributed by people all over the world via the Internet, when such collaboration was still novel enough to merit naming the package after it. Bryan Henderson has been maintaining Netpbm since 1999. In addition to packaging work by others, Bryan has also written a significant amount of new material for the package. For detailed credits of the pnm package, please see the netpbm homepage.
Eberhard Mattes wrote the excellent TEX implementation emTeX. Of course, TEX itself was originated by Donald E. Knuth, and LATEX by Leslie Lamport, and countless others have contributed to these.
Dvips was written by Tomas Rokicki, and the emTeX implementation was done by Guido Sawade.