James Clark:

Original author of the SP suite, from which OpenSP is derived.

Henry Thompson:

Initial autoconf support for SP.

Cees A. de Groot:

Autoconf support for SP.

Matthias Clasen:

spcat, DTDDECL, CONCUR, improved support of Annex K, 

autoconf & automake setup.

Peter Newcomb, Epremis Corp.:

MessageModule, support for HyTime Amendment 1 (IS10744:arch PI)