More than once in my short tenure on the open source beat, I've found myself puzzled by the phrase "commercial open source." It's odd, at best, and an oxymoron at worst. Aren't "commercial" and "open source" diametrically opposed, after all?
Dan Woods, CTO and founder of Evolved Media, tackles that very question in Forbes' JargonSpy column. And he makes a lot of really good points. For example, he notes that as open source projects grow in size and popularity, they become commercial, and they do so in several different senses of the word.
First, they become funded by companies or foundations that pay their developers to continue the work. (I made a similar observation back in July.) The Linux Foundation pays Linus Torvalds. Google pays Samba developer Jeremy Allison. Sun Microsystems is paying myriad developers to continue work on Java and Solaris, among other things. And those are just the first few that come to mind.
Popular open source projects also become commercial in that they are "productized" (think Red Hat or Novell). They are commercial in terms of business model (marketing tool + development methodology + support strategy). Finally, Woods says, they are commercial because consulting firms have organized to advise businesses how to best put them to use.
Maybe "commercial open source" isn't an oxymoron after all.