At last week's Open Source Business Conference, the topic of the day was, as one might expect, open source. In contrast to past years, however, there was less of the "we're a commecial open source founder\/investor, and we're inventing the future" (thankfully) and much more end user-oriented open source discussion.A pleasant surprise about these end user discussions was the extent of their open source use. Many discussions about open source by end users ends up focusing on how they are applying Linux in their data centers. Not that this isn't a valid use of open source, but by now this isn't exactly hot news.There were a couple of end user stories that I feel bear commenting on. The first was a presentation by the CTO of Paypal. As you might expect, Paypal has, by its very nature, enormous reach and scale -- on the order of 140 million users (of which I am an occasional one). Naturally, at this level of use, the company has architected an infrastructure based on commodity servers running Linux. As you might expect, lots of the CTO's effort goes into designing redundant systems to insulate the company against all types of failure, whether individual pieces of hardware or entire data centers. Certainly, Paypal uses open source software in its redundant infrastructure.I had the opportunity to have lunch with the CTO, Matthew Mengerink. What struck me during our conversation is how he has tuned his organization and development practices to take advantage of open source. Paypal has a laboratory where developers get a chance to experiment with new applications. Examples cited by Mengerink included a Paypal\/MySpace mashup designed to allow political contributions. The lab uses open source extensively as a way of facilitating creativity. By making it easy to obtain, modify, and (my term, not Mengerink's) waste software, Paypal employees are free to imagine applications unbounded by capital expense issues; with open source they can focus on thinking up value-add apps without having to wait for budget approval. In a rapidly-changing environment like that which Paypal operates in, the agility open source offers is a real benefit.I took a slightly different message away from one of the keynote speakers, Steven Pearson of CBS Interactive. He made much of the challenges CBS faces in terms of traffic, driven by events like March Madness. Again, like Paypal CBS leverages commodity boxes and Linux to scale at an affordable price.Little-commented upon was another slide he showed which listed some of the open source products CBS depends upon. Among them were PHP and Perl. Scripting languages are kind of the poorly-respected siblings of enterprise-approved languages like Java and C++. While looked down upon as being insufficiently manly (and, frankly, insufficiently complex so as to justify the "enterprise" label), scripting languages are incredibly widely used throughout the web world; in fact, they are much more widely used than most people (read: CIOs) apprehend. I found it interesting (and a bit heart-warming) that CBS Interactive, home of March Madness, has scripting languages powering at least part of their infrastructure. It gives one pause to consider how many architecture decisions are driven by technical prejudice and not by appropriate tool selection.Both Paypal and CBS Interactive, of course, are representative of a breed of enteprise users whose economics, driven by enormous scale, dictate use of open source. On the other hand, open source appears to working for them, very nicely, thank you very much. It might make you wonder whether you should be moving more aggressively to free software, even if you don't face the same challenges of economics and scale.