Sun Microsystems finds itself involved in another intellectual property lawsuit, this time with a US-based company that says Sun and its StorageTek unit have committed copyright infringement and fraud.

Netbula, which offers internet development tools, has filed suit against Sun and Storage Technology (StorageTek) in the US District Court for the Northern District of California in Oakland for unlawful use of its core technology in their LibAttach software, according to the plaintiff.

Netbula also claims that Sun and StorageTek breached a contract Netbula has with the companies and misrepresented their use of Netbula's technology, part of its main product line PowerRPC, in their infringement of copyrights. PowerRPC is a cross-platform client/server development kit for various versions of Windows, as well as for Unix and Java.

Sun announced it would purchase StorageTek in June 2005, but Netbula is suing the two as separate companies because the copyright infringement began when they were still individual entities, said Vonnah Brillet, the plaintiff’s attorney.

Brillet said Netbula's president Don Yue developed software and sold a licence for it to StorageTek when it was a standalone company. At one point when he asked about whether StorageTek was still using the technology, he was told the company was not, she said.

However, some time after that, someone from StorageTek asked Yue for updates to the technology, which proved that the company was still using it, but not paying for the license, Brillet said.

Netbula tried to resolve the issue with Sun before filing the suit to no avail, the company said. It is seeking an injunction to stop Sun and StorageTek from using its technology. The lawsuit also seeks financial restitution.

Sun is currently embroiled in another intellectual property suit over patents. Earlier this year, startup company Azul Systems sued the infrastructure vendor in a defensive move after Sun threatened the company with litigation for patent infringement and misappropriation of trade secrets.

Azul called Sun's charges unfounded and sued for declaratory relief against the accusations and the threat of litigation. Azul said Sun would file a lawsuit unless granted partial ownership of the company. Sun eventually countersued Azul in May for patent infringement. The cases are still pending in California.