For its part, Check Point’s website states that it is "committed to the Snort open-source community, and we look forward to growing the Snort solution and the Snort community in the future."

But the fact is, not all open-source security software has remained open. A software package called Nessus was initially released under an open-source license in 1998, but the latest version (3.0) has been released under a commercial license (earlier versions remain available as open source)—though it is still free to users. Nessus’s original developer, Renaud Deraison, who, like Roesch, has started a company (Tenable Network Security), says his commercial customers pressured him to close the source. "Many of them had prohibitions against [open-source] software or had to jump through legal hoops to get permission for it," he says. "What they want is quality, free software. The license is less important." Though Nessus’s shift has brought criticism from some open-source advocates on discussion websites like Slashdot.org, Nessus usage seems not to be affected—at least not yet.

Meanwhile, CIOs—who are constitutionally skeptical of vendor promises—are worried about Check Point’s purchase of Snort. "It’s definitely a concern," says Kirk Drake, vice president of technology for the National Institutes of Health Federal Credit Union, which uses Snort and Sourcefire’s add-ons. "But it’s no different from what we’ve seen before. We buy a good product, and it gets bought by another company and the product can change. And the pricing changes."

According to Roesch, those who see mixed source as a Trojan horse for an inevitable march back to proprietary software are underestimating the power of the open-source community. "Check Point got one of the most tested and deployed code bases in the world, and if they manage it carefully they’ve got the community too," says Roesch. "I would argue that the goodwill generated by Snort among users and developers probably outweighs the value of [the proprietary software], and I think Check Point believes that as well." In other words, continuing to support an open Snort will cost Check Point less than alienating the community by closing the source.

The Trojan Horse Scenario

No one in the open-source community faults Roesch or Check Point for making money from open-source software. After all, "free as in free speech, not free beer" is the mantra of Richard Stallman, the father of the free software movement (now more widely known as open source). But the open-source community, though far from monolithic, can agree on one thing: No one likes companies that would try to use open source as a Trojan horse for fee-based proprietary software.