IBM’s been working on its WebSphere based platform-as-a-service for years now. GigaOM first reported a public beta of the service way back in 2009. This week IBM gave its SmartCloud portfolio of service a big push, including a general availability version of the PaaS. It enables developers to create Java applications that can be hosted either on IBM’s public cloud, or on-premises as a private PaaS.

So what makes it different from all the other PaaSes out there? Middleware.

Most other PaaS solutions are aimed at startups and independent software vendors. IBM is going after enterprises that need to build applications Emphasizing Java and WebSphere instead of Web application frameworks like Ruby on Rails allows the company to go after companies that want to build enterprise applications that integrate with systems such as SAP, PeopleSoft and Siebel.

CloudBees and Red Hat’s OpenShift, which includes a service called Flex for deploying existing JBoss applications to the cloud, are some of the few PaaS providers considering enterprise middleware needs. I’ve heard little developer buzz around OpenShift yet, but it’s still in the developer preview stage. Red Hat does have the chops to pull off something interesting. CloudBees notably includes the option to deploy to private cloud infrastructure. And of course Oracle’s Java platform-as-a-service will integrate WebLogic and Oracle’s own Fusion line, but Oracle doesn’t have a product out the gate yet.

Vmware’s open source Cloud Foundry project is one of a few other options for building private PaaSes. VMware has its own public cloud service based on Cloud Foundry, but the company has made its tools available for other companies to build services.

One company that has done just that is AppFog, formerly known as PHPFog. In an interview, PHPFog founder Lucas Carlson told me that PHPFog built the PHP support for Cloud Foundry and contributed it to the open source project.

Carlson explained that there are at least three layers to a PaaS: On the top there’s the interface layer, which includes billing. Then there’s the middle layer that includes application life cycle management. Then there’s the bottom layer that interacts with infrastructure the PaaS is running on. Cloud Foundry provides only this middle layer, Carlson says. VMware’s Cloud Foundry based public cloud provides only a command line interface. That gives companies like AppFog, which is considering offering some sort of an on-premises offering, some room to innovate and distinguish themselves on the top layer.

It appears that IBM is trying to offer each layer of the PaaS for its SmartCloud customers.

Carlson says that in the beginning PaaS services distinguished themselves by offering a particular language or technology no one else was offering. He says dotCloud raised the stakes by offering multiple languages and databases. So other companies, including Heroku, Engine Yard and PHPCloud have followed suit.

Carlson thinks on-premise offerings will be the next must have feature for PaaS offerings and that user experience and developer ecosystems will be where the real differentiations. At the moment, IBM only supports the Java language, but WebSphere provides a large developer ecosystem. And of course it has the on-premise offering. What remains to be seen is how the user experience holds up.

Services Angle

In the Forrester’s report on Platform-as-a-Service the firm noted the dearth of enterprise ready PaaS providers on the market. At the time, it identified only Microsoft Azure and Salesforce.com’s Force.com platform as real enterprise contenders. That’s going to change. In addition to IBM’s offering, Cloud Foundry, OpenShift and CloudBees are all approaching enterprise worthiness if they’re not there yet.