appMobi announced openBuild this week, a free cloud service that makes it easier for HTML5 developers to optimize their apps for all the different app stores out there.

While HTML5 may be able to run both iOS and Android, actually deploying an app written in the language in the App Store or Google Play, not to mention the Chrome Web Store and Nook, is an entirely different matter.  So-called hybrid versions of an application (the HTML5 code plus a wrapper) have to be created for each individual marketplace, and openBuild aims to eliminate a big portion of the time and resources invested into this task.

As appMobi explains, “using the openBuild packaged Ruby library (called a ‘gem’), developers can create completely scripted cross platform app builds from within Ruby-based environments like Heroku and EngineYard, or even from their own computer. Unlike other hybrid app build services, like Adobe’s PhoneGap:Build, openBuild is completely free, and there is no limit to the number of apps that developers can build or publish. A fully featured Heroku add-on that integrates appMobi’s Web services into Heroku’s platform is under development as well.”

Up until now openBuild was only available via appHub, appMobi’s online portal and control center. It’s now accessible as a web service alongside a number of others such as the 1Touch e-commerce payment system and the PushMobi cloud-based ad service.

appMobi has a lot of faith in HTML5, and the firm seems to be gunning for a head start with the language still establishing itself as a cross-platform standard. Earlier this year appMobi rolled out v1.0 jqMobi, a  jQuery alternative that’s based on HTML5 rather than JavaScript and offers greater  performance than its more widely-used peer. Version 1.0 introduced expanded functionality and improved tablet support.