From the Raven website:
“As a result of the enormous popularity of the DOOM * source
code, we are extremely excited to see what the gaming public can do
with the Heretic and Hexen code,” says Brian Raffel, vice president
of Raven Studios. “It is our hope that people will create such
modifications as GL Heretic and GL Hexen and support higher
resolutions, greater multiplayer capabilities, mods, and ports to
new operating systems like BeOS and Linux. The possibilities are as
endless as the community’s imagination.”