Authors:

A critical factor in its success was that the X developers were willing to give the sources away for free in accordance with the hacker ethic, and able to distribute them over the Internet.

Eric S. Raymond (2001). “The Cathedral & the Bazaar: Musings on Linux and Open Source by an Accidental Revolutionary”, p.12, "O'Reilly Media, Inc."
A critical factor in its success was that the X developers were willing to give the sources away for free in accordance with the hacker ethic, and able to distribute them over the Internet.