BLSH, you need to read a little further down the article you posted:
"These types of cases generally involve bystanders overhearing conversations of corporate insiders and then trading on the information learned. Because the bystander has no duty to the corporation or anyone else, he may trade on the information without running afoul of the prohibitions against insider trading. Essentially, the bystander does not become a corporate "insider" merely by overhearing non-public information."
http://www.meyersandheim.com/insider_trading.html
As a further clarification, there is this:
"However, between these two extremes of a bystander with no duty to the corporation and a corporate officer with a clear duty to the corporation stood a whole group of people such as printers, lawyers and others who were involved in non-public transactions that did not necessarily have a duty to the company whose securities they traded. To address this group of people the courts developed the misappropriation theory. The misappropriation theory covers people who posses inside information and who are prohibited from trading on such information because they owe a duty to a third party and not the corporation whose securities are traded."
"These types of cases generally involve bystanders overhearing conversations of corporate insiders and then trading on the information learned. Because the bystander has no duty to the corporation or anyone else, he may trade on the information without running afoul of the prohibitions against insider trading. Essentially, the bystander does not become a corporate "insider" merely by overhearing non-public information."
http://www.meyersandheim.com/insider_trading.html
As a further clarification, there is this:
"However, between these two extremes of a bystander with no duty to the corporation and a corporate officer with a clear duty to the corporation stood a whole group of people such as printers, lawyers and others who were involved in non-public transactions that did not necessarily have a duty to the company whose securities they traded. To address this group of people the courts developed the misappropriation theory. The misappropriation theory covers people who posses inside information and who are prohibited from trading on such information because they owe a duty to a third party and not the corporation whose securities are traded."

