In my previous column, I touched on the issue of what constitutes an open-source vendor. Ask Andy Astor that question, and his answer is a shrug. "Honestly," he says, "who cares?" To Astor, there are really two broad categories of companies with respect to their relationship to open-source code. Some are users. Others are joiners.

Mind you, Astor's views on this subject are notoriously controversial. His company, EnterpriseDB, sits at the crossfire of the debate I touched upon last week. EnterpriseDB markets a product built on top of the PostgreSQL database, and it does good business. Since I last wrote about EnterpriseDB in late 2005, it has grown into a worldwide operation with more than 100 enterprise customers. The catch? While PostgreSQL is open source, the EnterpriseDB software is closed and proprietary.

To Nat Torkington, that makes EnterpriseDB "a tricky boundary case." In the O'Reilly Radar blog entry that I discussed last week, he even questions whether it's appropriate to invite the company to the O'Reilly Open Source Convention. "I find it hard to justify turning away a good open-source project to feature a closed source project, regardless of whether it runs on open source or not," he writes.

Astor says he has nothing to hide. Seth Grimes' comments notwithstanding, he was quite sanguine about EnterpriseDB's business model when I met with him last week. In his view, his company shares as much in common with Microsoft as it does with MySQL. "EnterpriseDB is an enterprise software company that happens to be built on open source," he says, "rather than an open-source software company with its eyes on the enterprise."

How does Astor reconcile the discrepancy between open-source ethos and proprietary software business models? "I find it's useful to distinguish between code and companies," he says.

In Astor's view, open-source code is a fact of life. There's no going back to a world where open source doesn't play a role in the enterprise software market. And open source is forever. As soon as code is released under an OSI-approved license, it is open-source code, no two ways about it.

But what about companies? Different companies take advantage of the value inherent in open-source code in different ways. Red Hat distributes all its software under open-source licenses and brings in revenue using a pure service/subscription business model. MySQL offers an open-source version of its database software but offers the same software under a commercial license for customers who would prefer not to be entangled by the GPL. Still other companies use open-source code as the basis of proprietary products.

EnterpriseDB falls into the latter category, but does that make it any less of an open-source company than a company that adheres to a different business model? That's where Astor's users and joiners come in.