Nonetheless, Seager said that KeyBank's core mainframe is under no immediate threat of being evicted by a Linux cluster.

The lack of plentiful banking applications for Linux also hurts the operating system's prospects, especially since banks tend to buy off-the-shelf software rather than building it themselves, said Brent Biernat, assistant vice president of networking services at COCC, an Avon, Conn.-based provider of IT services to community banks and credit unions.

The application shortage was cited by one bank IT executive as a reason why she remains "very cautious" about Linux despite the technology's potential for cost savings. Sufficient availability of third-party applications and "robust operational monitoring support remains to be seen," said the executive, who asked not to be identified.