The recent collaboration between Rackspace and NASA on the open source cloud called OpenStack marks a turning point for open source software projects, which creative IT people have hidden away from their bosses for years.

RackSpace, a Web hosting provider, and NASA, the nation’s space agency — which has been developing a scalable, secure cloud for its scientists — agreed to donate their code to a non-profit, and 27 companies (mostly technology vendors) signed up to participate.

[login]For RackSpace, OpenStack is a chance to avoid getting locked in to some other vendor’s cloud software and to focus on what it does best — managing data centers, the company says. NASA, which has been under pressure from the government to cut its costs, gets access to new outside technology for free.

Has your organization been looking more closely at open source software? More have — it’s matured, it’s better supported and it looks more appealing since the recession, according to Jay Lyman, an analyst with The 451 Group. Another analyst, IDC, has boosted its prediction for how fast global revenue from open source will grow to over 22.4 percent per year.

But open source is not always the right decision.

Here are four advantages, and four disadvantages, of using open source software. Please add your own experiences in the comment section below.

1) Less cost

At the end of last year, The 451 Group surveyed 1700 users, and 83 percent of them said open source met or exceeded their expectations, including cost. The survey didn’t quantify cost savings, but even commercial products based on open source, like SugarCRM, sell for substantially less than their commercial competitors. SugarCRM’s price also includes support.

2) More flexibility

Not only do open source users have access to source code, but open source software is modular, which makes it a good environment for plug-ins that can make the software better suited to you, Lyman says. “No matter what happens to the vendor or the product, you’ve got a code base and you can keep using it.”

3) Better performance and reliability

Open source has proliferated through the software stack – from operating systems to databases to middleware to programming languages to applications — and there are more chances to tune it. More vendors and systems integrators participate in open source too — Microsoft, Intel, IBM, Accenture and Google, to name a few. “Customers will look to their suppliers to weed through the software — they don’t care if it’s open source, and they shouldn’t have to,” Lyman says.

4) Avoiding vendor lock-in

The dangers of tying yourself into someone else’s code — and paying for expensive licenses to hang on to it — receded as more software was developed for the Web, but with the rise of cloud computing, those concerns are back. Look no farther than Rackspace, which has pledged that OpenStack will be designed, developed and documented in the open.

And here are some disadvantages:

1) Expecting open source to be free

It’s free to use, but you still have to support it, and support costs can grow fast. You can either hire someone to help with support or do it yourself, but unless you’re comfortable with the variety of issues that can come up — installation, missing drivers, licensing (see below) and so on — and unless you know your way around the open source community, you’re better off hiring help.

2) Potential licensing difficulties

It’s important to know which open source license applies to your software, especially if you plan to redistribute any code. Organizations that support Linux can often help with this, and The Linux Foundation is expanding its help with licensing issues, says vice president Amanda McPherson.

3) The lack of champions

You need experts inside your organization who can show you how the open source community works.
“Unless you have a person who’s really into it and knows how to surf the forums and support themselves, it’s a difficult process,” Lyman says. “It can be rewarding, but it’s a painful learning process. Don’t be afraid to seek out help — I think there’s greater appreciation of that now (even on the forums). You can write elegant software, but it doesn’t matter if no one is using it.”

4) Thinking that open source is always best for the job

Sometimes it’s not. Factors to consider, in addition to licensing, support and implementation issues, are the maturity of the software, according to Forrester. How much are you able to customize the software? How much do you risk pushing it to do something it wasn’t designed to do?