Lumen Software is hoping to tap enterprises and software developers interested in taking an open source slant on the emerging software-as-a-service model. The company is offering up its Lumenation SaaS development platform — an open source take on proprietary SaaS development approaches used by Salesforce.com or Microsoft’s OfficeLive.

Lumenation is targeting its platform at developers that want to provide SaaS offerings to end-user customers, but want to develop with open source standard tools such as PHP and AJAX, running on a LAPP server stack (Linux Apache, PostgreSQL and PHP — a twist on the LAMP stack, which uses the MySQL database). Lumenation could also be used by large enterprises, looking to transform the delivery of corporate client/server applications as a Web-based network service.

Lumen says it is going after a critical mass of PHP developers — over 5 million worldwide — and burgeoning demand for SaaS; it cites an IDC survey, where 15% of SMBs said they’re considering a move to SaaS.

The company’s free Lumenation SaaS application server and software development kit allows users to create advanced Web-based desktop applications, with “graphical drag-and-drop, click and launch functionality,” according to the Lumen. The company also has a software development portal, where coders can download pre-developed application frameworks (for SMB, enterprise and educational end-users) and share their work.

The Lumenation server and SDK are free to download. The packages include automated installer wizards for LAPP servers. Lumen offers paid commercial support packages for its software