Apprenda, a cloud middleware start-up, has released SaaSGrid Express, a free, downloadable version of its flagship SaaSGrid application server for software-as-a-service (SaaS).

SaaSGrid Express is supposed to be a complete foundation for delivering .NET applications as a service and you can't beat the price. The package, essentially three servers and a billing system, is supposed to be enough for a few hundred end users.

Apprenda's reason for being is to save others from having to invent and maintain their own SaaS architecture and delivery systems. For its trouble it would like to become the de facto standard.

According to CEO Sinclair Schuller, "Apprenda is enabling software engineers to be devoted solely to the value their applications provide, without having to worry about all of the business and technical challenges of delivering their software-as-a-service."

Apprenda isn't stinting much on Express. It's supposed to have all the main features and functions of the commercial SaaSGrid.

The company says applications built on top of the thing inherit the architectural qualities expected of mature, delivery-efficient cloud offerings without the middleware bother. It claims current SaaSGrid customers have seen engineering time and costs drop 50%-70%.

Existing .NET applications can just hop on. SaaSGrid Express is supposed to modify and transform their single-tenant code base into single-instance, multi-tenant widgetry that can be scaled-out as needed.

Besides billing Express also provides stuff like metering, subscription management, application lifecycle management, cloud control and customer provisioning.

Licensed SaaSGrid users pay a per server/per month fee, and have customization and branding capabilities, additional features and zero functional limits. The pricing scheme includes free access to maintenance and software upgrades and comprehensive customer service based on the number of licensed servers.

Apprenda says it's different from conventional licenses tied to the growth of the user's SaaS business.

In November New Enterprise Associates (NEA) and High Peaks Venture Partners put $5 million in the company. NEA of course has backed Salesforce.com, WebEx, XenSource and Juniper Networks. Apprenda got $1 million in 2007.

It claims only 7% of software companies have gone SaaS so far. Based on Gartner's calculations Apprenda expects the SaaS application market to be worth $14 billion by the beginning of 2014.

The firm recently released a SaaSGrid API for Silverlight that's supposed to remove a lot of the complexity in using Microsoft's single-tenant client-side platform as the front-end of an SaaS application.