Three companies that manufacture IBM-compatible mainframe hardware and software have agreed to drop antitrust complaints filed against IBM in the U.S. and Europe. Big Blue remains the subject of antitrust probes by the U.S. Department of Justice and the European Commission.

T3 Technologies and Neon Enterprise Software both have withdrawn their actions, IBM said in its most recent quarterly report. A third company, TurboHercules SAS, which develops open source mainframe emulation software, has also dropped a complaint against IBM, according to Bloomberg.

Neon originally filed a lawsuit against IBM in December of 2009 in U.S. District Court in Texas, claiming IBM interfered with its efforts to license its zPrime emulation software. Neon also filed a complaint against IBM with the EC in June 2010. In its SEC filing, IBM said it has settled the Texas lawsuit and that Neon has agreed to drop its complaint in Europe. Neon has agreed to stop selling zPrime. IBM said the settlements did not involve payment of any funds to Neon.

T3 joined an antitrust lawsuit against IBM in U.S. District Court in New York in January of 2008. The court dismissed the suit in 2009, prompting an appeal by T3. The cloner agreed to drop the appeal in May, IBM said. T3 also has withdrawn a complaint it lodged against IBM with the EC. "This litigation is concluded," IBM said.

The company isn’t completely out of the regulatory woods, however. Its quarterly filing states that the Justice Department is continuing to investigate it for possible antitrust violations, and that DOJ has requested documents from its litigation with T3.

The EC is also continuing its investigation of IBM “regarding possible infringements of European Union competition law,” the company said in its filing. IBM shares were off .29%, to $177.54, in afternoon trading Wednesday on the New York Stock Exchange.

At the 2011 InformationWeek 500 Conference, C-level executives from leading global companies will gather to discuss how their organizations are turbo-charging business execution and growth--how their accelerated enterprises manage cash more effectively, invest more wisely, delight customers more consistently, manage risk more profitably. The conference will feature a range of keynote, panel, and workshop sessions. St. Regis Monarch Beach, Calif., Sept. 11-13. Find out more and register.