SitePoint has this new article posted today that talks about "the business of PHP" - what kind of commercial software there is for PHP, how its "zero cost" mentality can sometimes hurt this, as well as a few that have broken the mold.

Perhaps an anomaly in the PHP landscape is, despite the massive adoption of PHP as a software development platform, the relatively small ecosystem of commercial software offerings that exist within it. One might easily put this down to PHP being an open source - and largely free - product. People who use a "zero cost" platform generally have little inclination to pay for software that runs on it.

I'd venture that the majority of professional PHP developers (and I use that term loosely; referring to people who earn a living coding PHP) work with / in some kind of client services entity. [...] Close behind that group would be those developers who build solutions "in-house" for an organization. Nonetheless, there is a small - and growing - section of the PHP community which focuses on developing proprietary software for the platform. I find their business models, and the challenges they face, fascinating.

He mentions the following projects: vBulletin, Cerberus Helpdesk, JpGraph, and the PHP AdWords API Lib.

I know there are more than just these that are having a great amount of success with different business models when it comes to PHP scripts - anyone have any others worth mentioning? Maybe one with a unique business model?