https://letmegooglethat.com/?q=microsoft+calls+linux+cancer

The original interview is no longer available, but here are references.

Microsoft CEO and incontinent over-stater of facts Steve Ballmer said that “Linux is a cancer that attaches itself in an intellectual property sense to everything it touches,” during a commercial spot masquerading as a interview with the Chicago Sun-Times on June 1, 2001.

Ballmer was trying to articulate his concern, whether real or imagined, that limited recourse to the GNU GPL requires that all software be made open source.

“The way the license is written, if you use any open-source software, you have to make the rest of your software open source,” Ballmer explained to an excessively credulous, un-named Sun-Times reporter who, predictably, neglected to question this bold assertion.

https://www.theregister.com/2013/08/24/top_10_steve_ballmer_quotes_from_microsoft_history/

“Ballmer: I may have called Linux a cancer but now I love it” https://www.zdnet.com/article/ballmer-i-may-have-called-linux-a-cancer-but-now-i-love-it/

“Former Microsoft CEO Ballmer does about-face on Linux technology” https://www.reuters.com/article/us-microsoft-ballmer-linux-idUSKCN0WC2RA/