SAN FRANCISCO (Reuters) - Now, they mean business. Developers of systems and software for the Linux operating system - which made its name as free alternative to Microsoft Corp.'s software - are now focused on its commercial prospects. The first LinuxWorld trade show a few months ago was seen as a major coming out party for the upstart operating system, but this week's show is boasting a number of product launches and nearly twice as many people. About 20,000 people are expected to attend, up from the 12,000 who came to the show in March. Many companies will announce products this week aimed at making Linux more friendly for electronic commerce, seeking to prove that Linux is a valid alternative to Microsoft Corp.'s Windows NT software for some applications.