The two will be sentenced in November, along with four other defendants who pleaded guilty in Milwaukee in April.
Rockwell Automation produces, among other products, specialized factory management software. The majority of the software applications sold by these defendants on eBay had retail prices ranging from about $900 to $11,300.
From September 2003 to September 2004, Koster offered counterfeit software in 105 or more online auctions, receiving a profit of more than $23,000, the DOJ said. The retail value of the software was more than $5 million.
From December 2003 to August 2004, Yamamoto initiated at least 92 auctions, for a profit of $6,000, the DOJ said. The retail value of the software was about $543,000.
Including Monday's pleas, the DOJ has gotten nine convictions involving eBay auctions of counterfeit Rockwell Automation software. In addition to six pleas in Wisconsin, there have been two convictions in the Eastern District of Michigan and another in the Southern District of Indiana. The combined retail value of the counterfeit software in all nine prosecutions is approximately $30 million, the DOJ said.