DL2

DeskLink2

An open source TPDD_server written in plain C.

Originally there was a commercial MS-DOS product named Desk-Link from Travelling Software.
Desk-Link

Then Stephen Hurd wrote a new work-alike he named dl - DeskLink for *nix.
dl 1.0 to 1.3

Then John Hogerhuis developed it a little further and called that dlplus
dlplus
retroactively versioned dl 1.4 but it doesn't say that itself

Currently Brian K. White has developed it further and is calling that dl2.
dl2