Most open source software projects come to life because someone is trying to scratch an itch.

Some group of coders or a team of academics or a fast-moving startup will build some software that solves a very real computing problem, and then they'll open source the code, sharing it with the world at large. Maybe, the coders are trying to help the larger world of software developers, believing that others will find the code useful too. Maybe, they're trying to get more eyes on their code, hoping that others will contribute bug reports and fixes to the project. Or maybe, as is typically the case, they're trying to do both.

The popular data-crunching tool Hadoop is a great example. Doug Cutting and Mike Cafarella started Hadoop to solve scalability problems they had with their open source search engine software Nutch. Then Yahoo saw the work they were doing, realized it would be useful, and hired Cutting to develop it further. Soon, other companies like Facebook and eBay joined in as well. Today, Hadoop is used by countless companies to crunch data, and several commercial outfits have sprung up to support and develop the software and its ecosystem.

There are a nearly endless number of open source projects that have evolved along similar lines, including the Apache web server, the Ruby on Rails programming framework, and, of course, the Linux operating system. But in recent years, we're seeing many old school tech companies–companies that predate the recent open source revolution—use open source in very different ways. Now, companies like Microsoft, Cisco and Salesforce are creating new open source projects mainly as a means of promoting new or existing products and services.

>Now, companies like Microsoft, Cisco and Salesforce are creating new open source projects mainly as a means of promoting their existing products and services.

A prime example is Salesforce Wear, an open source project started by Salesforce.com earlier this summer. Basically, this is a collection of open source tools for developers who want to build applications for smartwatches and digital eyewear such as Google Glass. But Salesforce didn't start this project because it wanted to develop wearable applications for its own employees. It started the thing to simply promote its own products, to encourage developers to build wearable applications that plug into its existing array of cloud services.

It's a less organic approach to open source, and we're still waiting to see how successful such projects will be. Will developers outside of the founding companies contribute to these projects in big ways? Will people use the code in big ways? It's hard to tell. "The question is whether you can 'boy band' an open source project," says Jim Zemlin, the director of the Linux Foundation, the non-for-profit that oversees Linux—the granddaddy of open source project—as well as a handful of these new-age projects from the likes of Microsoft and Cisco. But many big names are at least trying to make this work.

Cloud Foundry, an open source cloud computing platform originally created by VMware, is another example. Whereas the open source cloud computing system OpenStack was created by NASA with the help of Rackspace and Anso Labs to solve its own private cloud needs, Cloud Foundry was created by a company that wanted to sell it as a service to other companies. And it just happened to come along at a time when many companies were looking at open source alternatives to VMware's flagship software tools.

As with Salesforce Wear, it's hard not to see this as a marketing ploy—or as a hedge against younger, nimbler companies. But Zemlin says that nowadays, open source is most often used simply because it's a faster, cheaper, and better way of building software. It helps to have more eyes on the code, more people contributing to the cause. "Sony says that 80 percent of the code in its phones is now open source," he says. "Companies realize that open source is a better way to build infrastructure, and that frees them up to focus more on the other 20 percent of the code, which is the secret sauce."

In many cases, Zemlin says, open source is playing the role usually taken by standardization bodies. Instead of a large group of people decided on a specification for new products, the open source developers provide a common base layer or building new products. He gives two recent Linux Foundation projects as examples: the OpenDaylight Project, a collaboration between networking companies such as Cisco, Juniper, HP, and many others, and AllSeen Alliance, an "Internet of Things" initiative based on technology open sourced by Qualcomm that now counts Microsoft amongst its members. "Providing a huge standards document to a light bulb manufacturer won't help it make better, cheaper bulbs," Zemlin says. "But if you hand them the open source code, then they can just start doing it."

Like Salesforce Wear and Cloud Foundry, these projects are still finding their way in the world.. But at least one "boy band" project has proved an enormous success: Google's Android operating system. It was created to serve Google's business needs, and it worked because it provided phone makers with a free OS they could load on their devices, letting them sidestep for-pay OSes from the likes of Microsoft.

That may be a unique open source play. Unlike a Microsoft or a VMware, Google is itself a newer, nimbler company, and it unloaded Android on a market that didn't really have an open source alternative to Apple's iPhone software. But one thing's for sure: the number of reasons to create open source software continues to grow. In many cases, it's because it was simply the best way to solve a very real problem. But sometimes, a big-name company may have another agenda in store.

Correction 11:00 AM EST 07/09/14: An earlier version referred to the OpenDaylight Project as Project Daylight.