De A arte da programação Unix (grifo nosso):
After the [1974] paper, research labs and universities all over the world clamored for the chance to try out Unix themselves. Under a 1958 consent decree in settlement of an antitrust case, AT&T (the parent organization of Bell Labs) had been forbidden from entering the computer business. Unix could not, therefore, be turned into a product; indeed, under the terms of the consent decree, Bell Labs was required to license its nontelephone technology to anyone who asked. Ken Thompson quietly began answering requests by shipping out tapes and disk packs — each, according to legend, with a note signed “love, ken”.
Há muito mais informação relevante nesse capítulo; seu título é "Origens e História do Unix, 1969-1995". Leitura altamente recomendada (juntamente com o resto do livro!):)