In fact, cost is not the major factor at Opus. "We often look to open-source projects as a way to get our feet wet with a specific technology so we can see if a product type meets our needs and the needs of our clients without spending money on the corresponding commercial solutions," Sherwood says. Currently Opus is looking at open-source products for SAN functionality, network management and network control.

Open source is also a way to solve a problem, add a new service or perform some other function that has not yet been budgeted for, or "has not been proven as truly useful and worth pursuing," he says.

Because open-source projects, in general, "do not move forward at the pace of the commercial packages," Sherwood says, his company was looking at more development costs to add functionality or change open-source packages to meet its own needs. So one "hidden cost" of open source, he says, is what it takes internal developers or outside contractors to modify an open-source package. However, in some situations, "commercial offerings are far too costly or lack the necessary functionality required and, therefore, are not a good value. In these cases, open source may be a good solution."

Still, for the foreseeable future, most observers say that open-source will coexist with proprietary packages in the data center.

"As [open-source] packages become more reliable and feature-rich, their popularity will undoubtedly grow among businesses attracted to the relatively low cost of implementation," say EMA's Brasen. "It's unlikely, however, that open-source solutions will completely replace commercial products."