JBoss' low cost of ownership compared to competitors such as IBM's WebSphere and BEA's WebLogic has helped it win customers on multiple platforms, according to Steve Walli, vice-president of strategy at Boston open-source consulting firm, Optaros Inc.

Indeed, JBoss acknowledged in September while signing an alliance with Microsoft -- which has its own Windows-only application server -- that about half of its customers were using JBoss to work with Windows Server in a .Net environment.

Walli said that factor could complicate Red Hat's marketing strategy. But a user said it could motivate him to switch to Red Hat.

"I have wanted to switch from Windows to Red Hat for some time, but I am not familiar with Linux," said Jason Long, CEO and chief software engineer at Supernova Software and founder of the Houston JBoss Users Group. "This should lower that barrier and make it a more attractive option."

Computerworld's Heather Havenstein and James Niccolai and China Martens, of the IDG News Service, contributed to this report.