Some observers question whether open-source frameworks really deliver the benefits they're said to offer -- such as portability among clouds providers. "Eucalyptus replicates some of the Amazon APIs, but if you're using something on Amazon [that] Eucalyptus doesn't support, you're out of luck," says Roby. "Similarly, if you're trying to run Java apps and using the Spring [application development] framework, you've got a fair amount of support." But as soon as a customer begins using features, such as data storage, that can't be accessed via Spring, those features may not run correctly with a different provider. Without the ability to move underlying services as well as the application code, he says, "you don't have any portability."
With open source, users (or a group of users) theoretically could take the source code and tweak it to meet their own needs if a vendor can't or won't. However, few users would want to do that, says Roby. "If you're a big telco, maybe you are interested in being able to change the code... but most organizations wouldn't do that. The last thing they want is to have their own specific variant of the product" that they would have to support, while losing the ability to take advantage of upgrades from others in the community, he says.
Creating a unique open-source "fork" is usually not something you want to do "unless you absolutely have to," agrees Conway, noting that the fork could stagnate without contributions from others.
Much buzz surrounds open source, but proprietary frameworks such as Microsoft Azure or Salesforce.com's Force.com can be better choices "if you have specific needs and that platform already has built-in [elements] to make the job easier," says Shriram Nataraj, senior director in the cloud technology practice at Persistent Systems, a global software development firm. "If you're already a Salesforce customer and want to migrate part of your workload onto a different platform, Force.com can be a very good option for you. If you're already an Office 365 customer and have workloads on [Microsoft's .Net framework]... it makes sense to go towards Microsoft Azure."
Good fits for open-source frameworks tend to include experimental cloud applications built by developers who are comfortable with newer, open-source tools. Other likely candidates include applications deployed by organizations such as universities or research labs, which have the technical skills to learn and work with these new technologies, and/or the need for specialized capabilities such as massive databases or advanced analytics, says Roby.