The story of open-source software has largely been one of success to date. Open source has grown exponentially in popularity among Web users, and it's making headway in corporate application-development environments, even influencing the ways in which proprietary app vendors create and distribute their own products.

Still, open source won't be a tale of unmitigated growth. The answer to open source's challenges is, in a word, services.Open-source has moved steadily up the software stack, beginning with Linux on the operating system level and followed by infrastructure applications, databases, development tools, and enterprise applications. A good way to measure the shift in the IT market is to look at how open-source is affecting large, established IT players. Sun Microsystems has introduced its OpenSolaris initiative, Hewlett-Packard and SAP are supporting the open-source JBoss app server and MySQL database, and BEA Systems' a year ago launched Project Beehive, an open-source application framework and collection of run-time services for building enterprise Java applications. Even Microsoft has continued to promote its Shared Source initiative that provides its customers with access to the source code for projects including the Windows Installer XML, ASP.net samples, and Visual Studio.net Academic Tools.

But any phenomena that grows quickly from a grassroots following to a become a major market force will eventually be put to a greater level of scrutiny, a dynamic that played out a few years ago as the dot-com market was ruthlessly trimmed to a handful of survivors.

For open source, the challenges are many. Sure, companies can download as much software as they want, but how to they make it work together? How do companies track the open-source software that employees are downloading? How do they support mixed stacks of proprietary and open-source applications over the long haul?

Support and services are the keys to a successful Linux rollout, Aaron Graves, a Citigroup Inc. senior VP, said earlier this week at a LinuxWorld event in New York. "Business and IT managers need to understand that they're not out there alone," he said.

As if to emphasize this point, SpikeSource Inc., a provider of software testing, certification, and management services, Friday announced it has raised $12.9 million in Series A venture capital funding, led by Fidelity Ventures and the company's incubator Kleiner Perkins Caufield & Byers. Additional investors include Intel Capital and Omidyar Network, a fund co-founded by eBay founder Pierre Omidyar.

SpikeSource provides a test engine for application interoperability, which is what customers want, CEO Kim Polese said earlier this week at an open-source panel hosted by the Information Technology Association of America. "Open source is also a signal that users are outpacing vendors in terms of innovation," she added.

Companies that push the limits of what's typically done within corporate development environments need to know what's at stake when they consume open-source software, says Colin Bodell, chief technology officer of VA Software Corp., parent company of Open Source Technology Group Inc., which runs the open-source repository site SourceForge.net. "Every company involved with any code, whether open source or something they've licensed in, needs to be aware of their obligations," he says. This includes understanding the open-source licenses that apply to different projects and being able to track use of open-source code.

These challenges aren't likely to derail the growth of open-source software. "For every commodity piece of software that's proprietary, there's either one open-source project doing the same thing, or there will be," Bodell says.

The rising demand for open-source components that can drive down costs within large IT operations is likely to be a tough transition for services firms. "Services firms aren't good at getting ahead, they tend to jump on the bandwagon," Bodell says. "My concern is the bandwagon is moving too damned fast." This could lead to a feeding frenzy where small, emerging service providers such as SpikeSource or open-source experts with a good idea are quickly gobbled up by more traditional service providers looking to the future.