Throughout 2006, Linux and open source continued their march toward the mainstream of enterprise software. Perhaps no one event exemplified this trend more than Red Hat’s acquisition of JBoss in April. With JBoss’s Java technologies under its wing, Red Hat is no longer merely a Linux vendor; it’s become an open source powerhouse, able to offer its customers a complete application software stack.

The year’s successes for open source did not come without conflict, however. The roster of companies involved in open source now reads like a list of the world’s largest enterprise software vendors. For once, key open source projects are backed with real dollars, but there’s also an unfortunate downside. With the stakes so high for the industry at large, developers and users of open source software are often left to wonder, “Who are my real friends?”

Take Oracle, for example. A frequent contributor to the Linux kernel, Oracle has positioned the open source OS as a key platform for its database and applications software. And yet, in October the company announced it would provide cut-rate enterprise support for Red Hat Linux, a move seemingly calculated to undermine the leading Linux vendor’s core business.

Meanwhile, Sun Microsystems, though a longstanding opponent of Linux in the enterprise, has continued to move aggressively toward an open source model for all of its own software offerings. Jaws hit the floor in November when Sun announced it would license its crown jewels, the Java language platform, under the GNU GPL (General Public License). This was no lip service to open source. This was the real thing.

Novell, on the other hand, maintained its position as the second-largest Linux vendor throughout 2006. But when it shocked the industry in November by announcing an unprecedented intellectual property licensing pact with Microsoft, the community was left to wonder whether Novell had forsaken its commitment to open source principles, to say nothing of the terms of the GPL.

As usual, the community provided alternatives. In June, Ubuntu -- a popular, recent Linux distribution with a strong free-software ethos -- announced its first-ever “enterprise ready” release, backed by up to five years’ support from Ubuntu’s sponsor company, Canonical.

Perhaps the most significant work in open source in 2006, however, was the process of drafting the next version of the GPL, which continued throughout the year. Though not completed yet, Version 3 of the license is expected to include strict new rules regarding software patents and DRM (digital rights management) technologies, among other tweaks. Whether existing open source projects will transition to the new license in large numbers, and what impact that might have on the commercial open source industry, remains to be seen.

What is certain, now more than ever, is that community-based development and open source methodologies have transformed the software industry in a way that can never be reversed, and indeed is still gaining momentum. In the years to come, striking a balance between the open and the proprietary, the commercial and the free, will continue to be one of the most critical challenges for enterprise IT managers.