Plus: MCI names former AT&T exec president; SCO claims big bucks in Unix licensing deals; another Linux supercomputer cluster in the worksVerizon Wireless \u00a0this week was expected to turn up a nationwide "push-to-talk" service, thus becoming the second mobile operator to offer the walkie-talkie-type service. Until now, Nextel has differentiated itself with its push-to-talk service, which observers have credited for the wireless operator's industry-low customer churn rate. Analysts expect Sprint PCS to launch a similar service later this year. Push-to-talk lets customers connect directly with other push-to-talk users on the same network by pressing a button on their handset. Business customers can set up and manage group calling lists on Verizon Wireless' Contact Management Web site without going through customer service or a Verizon Wireless retail store, the carrier says. The monthly access fees for the service range from $60 to $220.After weeks of being on the defensive and responding to a series of allegations of wrongdoing by chief competitor AT&T,\u00a0MCI last week announced the appointment of a former senior AT&T executive as its new president. MCI named Richard Roscitt to serve as its president and COO, who will report to Chairman and CEO Michael Capellas. Roscitt brings more than 30 years of telecom experience to the company, having served most recently as chairman and CEO of ADC Telecommunications, and he is currently a member of the board of directors of the Telecommunications Industry Association. Before ADC, he was president of AT&T Business Services and president and CEO of AT&T Solutions. Roscitt will oversee MCI's core operating units and will be based in the company's headquarters in Ashburn, Va. Capellas said the company wasn't out seeking a COO. "This was a question of the right guy for the job," he said. "There was no other candidate considered." Roscitt will begin work Sept. 1.The SCO Group\u00a0predicted last week that it would book close to $12 million in revenue on Unix licensing deals with technology companies next quarter. The company said the revenue would come from its SCOsource licensing initiative, which was created in January to manage licensing fees for the System V Unix source code that SCO owns. SCO is in Unix license negotiations with a number of companies, according to a company spokesman. The revenue in question is expected to come from technology companies looking to secure the Unix rights, and not from Linux users signing up for its Intellectual Property License for Linux program. Last week SCO branched beyond licensing Unix to technology vendors when it created a new SCOsource product, aimed at Linux users, called SCO Intellectual Property License for Linux. SCO says the Linux source code violates its intellectual property rights and has offered its Linux license, at a cost of $699 per processor for server users.Another\u00a0Linux supercomputer cluster with Advanced Micro Devices' Opteron chip is in the works, this time for Los Alamos National Laboratory's nuclear weapons testing program. Linux Networx last week announced it has been selected to build the cluster of 1,408 dual-processor Opteron servers. The system, known as Lightning, will deliver theoretical peak performance of 11.26 trillion floating-point operations per second (FLOPS), the company said. The deal is worth $10 million, and Linux Networx expects to complete the system in September, Dean Hutchings, COO of the company, says. A number of Linux supercomputers have been announced over the past few weeks. Dell is working on what will become the fastest Linux supercomputer when it is finished later this year, with 17.7 trillion FLOPS of peak theoretical performance. IBM and Fujitsu also are developing Linux supercomputers that will be deployed next year with TFLOPS results expected to be similar to that of the Linux Networx system.