On May 23, Attachmate Corp. received clearance from the Department of Justice for its $495 million cash purchase of San Jose-based NetlQ Corp. The deal was announced in April. Seattle-based Attachmate is a privately held vendor of software used to link mainframes to PCs. The takeover removes ailing NetIQ from the ranks of publicly traded companies. NetlQ has struggled to integrate several acquisitions and faced mounting competition in the market for software used to manage corporate computer networks.