Tcpreplay has a bit of a different history than most open source/free software tools available today. Different because, tcpreplay has had multiple authors, some of whom have never even communicated over email.
Tcpreplay has had quite a few authors since it was first released back in 1999. One of the advantages of the BSD and GPL licenses is that if someone becomes unable or unwilling to continue development, anyone else can take over.
Originally, Matt Undy of Anzen Computing wrote tcpreplay. Matt released version 1.0.1 as part of the nidsbench toolkit sometime in 1999. Sometime after that, Anzen Computing was (at least partially) purchased by NFR and development ceased.
Then in 2001, two people independently started work on tcpreplay: Matt Bing of NFR and Aaron Turner of OneSecure. After developing a series of patches (the -adt branch), Aaron attempted to send the patches in to be included in the main development tree.
After some discussion between Aaron and Matt Bing, they decided to continue development together. Since then, two major rewrites have occured, and more then thirty new features have been added, including the addition of a number of accessory tools.