Laszlo Systems has released a framework to help developers place multiple applications in a single browser window and have them interact with each other, company officials said.

The new tool, Laszlo Webtop, is based on AJAX and runs on top of OpenLaszlo, an open source web development platform.

"These applications [in the Webtop framework] all have to be OpenLaszlo applications. That's how we get the tight integration and performance," said David Temkin, co-founder of Laszlo Systems. "There's a lot of interoperability. ... Elements of one application can be dragged into other applications, just like a real desktop. You don't get that integration normally on the web."

Unlike OpenLaszlo, Webtop is not free. Most businesses will pay at least $100,000, including licence fees, hardware and the cost of application development, company officials said.

Webtop also has a single sign-on function so users can log on to multiple applications with one password. Developers could place multiple applications in a browser with OpenLaszlo alone, but it requires writing more code, Temkin says.

"If you write a multiple-application desktop there's a lot of code to be written just to support that," he said. "The idea of having to implement a browser-based windowing system is not attractive to your average developer out there."

Webtop could be used to to deliver software as a service in various fields, such as communications, business intelligence and customer relationship management, Temkin said.

Roundarch, a partner of Laszlo, will use Webtop to help its clients build websites. "They're giving you a framework and an ability to create the next generation of applications, applications that talk to one another," said Charles Fiesel, managing director of Roundarch.

Laszlo this week also announced the 4.0 version of OpenLaszlo, which is available for download . OpenLaszlo users include Gliffy, an online program that lets users draw and share diagrams, as well as Wal-Mart and H&R Block.

The biggest change in the new version allows web developers to make interactive programs in a browser without using Adobe Flash Player. "It's just as interactive, just as animated, just as high performance ... but it doesn't' require the Flash Player," Temkin said.

That's not unique to Laszlo, though, says Jeffrey Hammond, a senior analyst at Forrester Research. "Just about every AJAX framework lets you use that," he said.

OpenLaszlo and Webtop should be compelling to enterprises because OpenLaszlo is free, Hammond says. But OpenLaszlo is difficult for many people to use because it requires knowledge of JavaScript, he said.

"The tooling experience leaves something to be desired," Hammond says.

AJAX tools are used to build rich internet applications, web applications that have the features and functionality of desktop applications. Competitors to Laszlo include the Google Web Toolkit, Microsoft's ASP.Net and Dojo, an open source platform supported by IBM and Sun.

Earlier this week, Adobe released Apollo, which seeks to go beyond AJAX by allowing applications to run offline as well as online.

The tight integration between Flash and Adobe products, including the Flex tool, makes it a good choice when creating applications that require complicated animation, Hammond said. Apollo, he said, also has the advantage of being able to build what appear to be standalone client applications that run without a browser window.

Temkin said he doesn't see Apollo as a direct competitor. "What Apollo is about is building desktop applications using web techniques," he says. "But they are desktop applications, they do require installation. ... AJAX is about delivering applications running in a web browser."