AppFog is taking a shot at the biggest cloud vendors with its new platform-as-a-service (PaaS) pricing model that charges users based on the RAM they need instead of capacity. The company has also announced a new platform for Web, enterprise and mobile developers.

The solution  gives users with free accounts 2 GB of RAM. Paid plans begin at 4GB for $100 per month and go to 32GB. Customers that require more RAM can purchase it for $22.50 per GB. The model seems to be working.  AppFog reports that there are more than 40,000 developers using the platform.

“Today we are in the early Hotmail days of PaaS with all the leading providers giving the equivalent of 15MB of space to run apps,” said Lucas Carlson, founder and CEO of AppFog.  “AppFog is doing to PaaS what Google did to email. We are giving developers 2GB of RAM for free to use any way they want, such as scaling their app with dozens of load balanced instances or running it across multiple infrastructures.”

AppFog claims it offers the most affordable and simplest pricing in the cloud. Aside from the pricing model, AppFogs new GA platform offers a number of other features  that differentiate it from similar services. For example, users are required to pay more to leverage services from multiple IaaS vendors. The service also makes it easy for users with free accounts to scale their applications. AppFog also touts the “best interoperability in the cloud,” promising zero-code migrations between different IaaS solution. The company claims deployment  to services like Amazon Web Service (AWS), Rackspace, HP and Azure takes 30-seconds. GA also supports several popular programming languages and frameworks such as Java, .NET, Node, Python, Ruby, PHP, MySQL, MongoDB andPostgres.

AppFog also allows users to run their own managed PaaS platform on-premise via OpenStack or VMware vSphere.  Earlier this month v2.0 of OpenStack-based PaaS Stackato was rolled out, also introducing a host of new features. One of the main improvements that the update brought with it is .NET support, alongside other enhancements such as increased automation and security.