Why not talk about SourceFire, Sleepycat, Splunk, Hyperic, Zimbra, and Astaro
All selling services and products around a very specific type of software, selling to a very specific market niche, leveraging both trademarks and non-GPL licensing to do so.
They're not selling the GPL software itself.
Take your Sourcefire example. They fund development by selling proprietary hardware and proprietary licensed IDS rulesets under trademarked names to an enterprise market niche.
Who isn't selling specific software to specific niches? Your choice of license isn't going to make you any more successful with a new word processor.
It's also not true that all successful open-source companies sell to enterprises. Tenable sells Nessus to consultants. Sleepycat sold Berkeley DB to OEMs and developers. Automattic certainly doesn't sell Wordpress to enterprises.
You're introducing a logical non-sequitur. That there is a niche isn't the issue, it's what the niche is.
Enterprise services.
The fact that they're also not actually selling GPL software (ie, an indirect business model), this all doesn't really disprove my point -- or the original authors.
All selling services and products around a very specific type of software, selling to a very specific market niche, leveraging both trademarks and non-GPL licensing to do so.
They're not selling the GPL software itself.
Take your Sourcefire example. They fund development by selling proprietary hardware and proprietary licensed IDS rulesets under trademarked names to an enterprise market niche.