A summary of Southern California-related business litigation developments during the past week.

Microsoft sues: Microsoft Corp. sued QDG Inc. for trademark and copyright infringment, claiming the Southland firm is selling unlawful knockoffs on one of Microsoft’s “most important software products.” In the federal lawsuit, the Redmond, Wash., computer software giant alleges that QDG, which has offices in Tarzana and West Los Angeles, is marketing a “counterfeit” of Microsoft’s MS-DOS 3.3, an updated and improved version its basic MS-DOS disk operating system. In addition to unspecified damages, the suit seeks an injunction barring QDG from selling the products and an accounting of its profits from the alleged counterfeit.