What's the opposite of open source? Hint: The answer is quite straight-forward. And it's not what some analysts and insiders would have you believe.

The definition of "open source" (as applied to software) is almost universally accepted as that of the Open Source Initiative. Per the OSI, "open source doesn't just mean access to the source code. The distribution terms of open-source software must comply with [certain] criteria" that are outlined on the OSI's Web site. Open-source software, per the OSI, is free, "free" as in "free beer" rather than necessarily as in "free speech," which latter usage of "free" carries with it certain responsibilities. Those responsibilities are "vitally important" according to Richard Stallman and other free-software movement proponents.There's nothing (so far as I can tell) in the free-software movement or in the OSI definition that says that open-source (or free) software can't be commercial. "Commercial," to me, means that involved persons or organizations have profit motives, that they derive financial or other tangible business benefits from their work on open-source (or free) software. "Commercial" is not the opposite of "open source."

And there's nothing (so far as I can tell) in the free-software movement or in the OSI definition that appoints "proprietary" as the opposite of "open source."

"Proprietary" is, however, the opposite of "free," of "free" as expansively defined as "do with it whatever you want," of "free" equated with "public domain." If you claim public-domain material as your own, you may be guilty of plagiarism or intellectual dishonesty, but you won't be infringing anyone's proprietary ownership rights.

"Proprietary" cannot be an opposite, however, of any term with a sense that implies restrictions. After all, restrictions, if legitimate, are imposed by someone who is empowered, who has the right, to impose them. That person or organization is empowered by some form of intellectual-property ownership that applies to the software. That person or organization has proprietary rights over the software.

Most open source, including most OSI defined open source, does indeed carry restrictions. Most open-source software comes with a license that specifies what you can do with it. That license may be "copy-left," requiring you to give back any modifications you make to the source code. The GNU General Public License (GPL) is an example. It may be very friendly in a commercial sense, allowing you to keep private (i.e., as your own property) your modifications. The very liberal (in the sense of nonrestrictive) BSD license has only a few, loose restrictions, but they are restrictions nonetheless. Any software licensed via the BSD license is someone's intellectual property. It is proprietary.

Many authorities get it wrong. They include the BSD source I linked to above, which wrongly equates "proprietary" with "commercial." Similarly, the GNU GPL definition seemingly matches "proprietary" with "anything not licensed under a GPL[-like] license." Authorities who get it wrong include, recently, ZDnet blogger Dana Blankenhorn, who explicitly differentiates "a proprietary vendor" from "an open source one" as if, for instance, open-source JasperReports software components magically aren't the property of vendor JasperSoft.

JasperSoft Community Edition software is covered by the GNU General Public License. The choice of license was JasperSoft, acting (legitimately) as "the copyright holder of JasperSoft software." The software is JasperSoft's property. The software is proprietary. It is also open source. "Open source" is not the opposite of "proprietary."

I haven't answered my opening question, "What's the opposite of open source?" The best answer is just as straight-forward as I claimed: it's "closed," not only in the usual sense of "you can't see the source code" but also in the sense "exclusive," that is, "exclusively for those who bow to my commercial interests."

I'm reminded of a much-covered Neil Young song, "Love is a Rose": "You lose your love when you say the word 'mine.'" There's plenty of love in the open-source movement: altruism, community, collaboration, and more. We're fortunate that you can still get all that open-source goodness -- the "mine-ness (but let's share)" -- that is afforded specifically by the sympathetic assertion of proprietary rights by intellectual-property owners who believe in open source.What's the opposite of open source? Hint: The answer is quite straight-forward. And it's not what some analysts and insiders would have you believe.