Apple Computer has gained the legal right to use the name "OS 9" in its current Macintosh operating system release.

Microware Systems sued Apple in September of last year, saying Apple violated the trademark of its own OS 9 operating system, which had been in effect for more than 20 years.

However, a US District Court judge in Des Moines, Iowa, Wednesday issued a summary judgment that dismissed Microware's claim under a doctrine of "fair use", both parties confirmed today. "Fair use permits others to use a protected [trade]mark to describe aspects of their own goods, provided the use is in good faith and not as a [trade]mark," US District Judge Robert Pratt wrote in his ruling.

George Leonard, Microware's chief financial officer, said the company has not decided whether to appeal the judge's decision. He added: "The OS 9 has been one of our products since the company was founded in 1978."

Microware's OS 9 is the trademark for the company's real-time operating system software licensed to OEMs (original equipment manufacturers) and used to run cellular telephones, wireless communications devices and other "smart" devices, the company said in court papers.

In his ruling, the judge said there is little chance consumers would mistake one product for the other because the operating systems are sold in different markets.