Here is a description of the situation from the article

What kind of science is this?
by Jim Giles, Nature 417, 216 - 218 (2002)

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But within the world of complex systems it is difficult to separate reactions to the man from those to his ideas. One incident in particular has driven a wedge between Wolfram and his former colleagues. The rule 110 proof was actually developed by Matthew Cook, a young mathematician who worked for Wolfram between 1991 and 1998. After leaving Wolfram's employ, Cook presented his results at a conference at the Santa Fe Institute. But details of the talk never made it into the conference proceedings. Wolfram took legal action, arguing that Cook was in breach of agreements that prevented him from publishing until Wolfram's book came out.

"We sympathized with Matthew," says one Santa Fe researcher. "Wolfram took a privatized view of science." Cook, now a graduate student at Caltech, says he cannot discuss the matter for legal reasons. Wolfram is similarly reticent - when pressed he describes the incident as "regrettable and best forgotten".

It is not the first time that Wolfram has annoyed complexity researchers, who feel that he routinely fails to recognize the contributions made by others. "He tends to acknowledge people in two-point type," says one researcher. Indeed, A New Kind of Science lacks conventional references to prior work - although scientists and mathematicians including Cook are acknowledged in the book's notes section.

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