Earlier this month, America Online announced that it was offering a software development kit for its instant messaging service, AIM. The kit, which the company is labeling “Open AIM,” allows programmers to modify AIM software so they can incorporate it into Web services or add new features to the existing interface. “We believe there’s a whole bunch of creativity and interest in the developer community to build new applications for our network,” says Justin Uberti, chief architect for AIM.

The move could encourage software developers to build innovative, new software based on instant messaging (IM) – one of the fastest-growing communication technologies, which already has some 25 million users in the United States.

But there’s a catch. Open AIM comes with some not-so-open restrictions, which could turn off many developers. For one thing, programmers aren’t permitted to build on software that operates with competitor’s IM programs, such as Microsoft’s MSN Messenger and Yahoo Instant Messenger. Second, in order to create software for a mobile device or to distribute modified software to large businesses, they must obtain a license through AOL.

There’s an alternative, though, to proprietary instant-messenging products such as the AOL, MSN, and Yahoo platforms – one with fewer restrictions and that has already produced a number of innovative applications, according to Peter Saint-Andre, executive director for the Jabber Software Foundation, an open-source IM network. He makes a comparison with another software realm: Jabber, he says, competes with commercial IM services in the way that Linux vies with Microsoft Windows.

One big area of open-source IM innovation is the integration of text and voice-over-the-Internet (VOIP), says David Reed, a professor in MIT’s Media Lab. And one such innovation using Jabber is the Gizmo Project. It’s sort of a home-grown* Skype, the wildly successful free software used primarily for making phone calls over the Internet. Like Skype, Gizmo Project combines audio and text communication, allowing users to chat and send and receive phone calls from a computer. But whereas Skype users can connect only with other Skype users, Gizmo lets people conduct free text and audio conversations with friends on different IM networks, says Michael Robertson, founder of the project. For instance, Gizmo and Google Talk – which uses Jabber for IM – will work together.

Gizmo provides audio conferencing for up to 99 people, compared with just 5 for Skype. Also, it has audio publishing capabilities, so a phone conversation can be recorded and posted to the Internet as a blog entry, says Robertson. Additionally, Gizmo connects easily to the standard telephone world, he adds. When someone calls Robertson, both his cell phone and computer ring simultaneously, and he can choose which to answer.

*Correction: In the original version we labeled the Gizmo Project as “sort of an open-source Skype…” In fact, while the Gizmo Project uses open-source components, the technology is not available under an open-source license.

The key to inter-operability and other features of Gizmo is that it uses both an open-source IM server, Jabber, and an open Internet voice server, called SIPphone. This means anyone can build software for it that connects to the text or voice network. In contrast, Robertson says, AOL, MSN, and Yahoo don’t share the specifications for their server or client software – which is why an AIM user can’t chat with someone using MSN Messenger. And while some software, such as Meebo and Trillian, have “reverse engineered” closed network protocols to seemingly combine the major IM networks, Robertson says, they merely supply a unified user interface; there’s no true inter-operability.

Beyond voice and text communication over the Internet, other applications have emerged that are a far cry from the traditional image of IM as a computer-to-computer chatting tool. A U.K. company called Trakm8, for example, uses the Jabber protocol and Global Positioning System to send text messages to mobile phones about the location of a car. The system also offers a feature alertings drivers via text messages if their car exceeds the speed limit.

Some investment banks have also adopted Jabber IM, building applications to fit their specific needs. Workers have multiple chat windows open at once, and when certain financial information pops up in one window, it can be routed immediately into spreadsheets containing financial models that, in turn, trigger buying decisions, Saint-Andre says.

Ideally, according to Gizmo’s Robertson, people should be able to send instant messages or make an Internet phone call as easily as sending an e-mail message. Someone who uses Microsoft’s free web-based Hotmail service, for instance, can transparently send messages to Yahoo Mail or Google’s Gmail. This inter-operability dates back to the early days of the Internet, when all e-mail servers were designed to use the same protocol, Saint-Andre says.

IM, however, started out as proprietary software and has stayed that way. Robertson wants to change that with initiatives like Gizmo. “The world I’m trying to create is one in which you have one screen name that works everywhere, very similar to e-mail,” he says. “That’s not the way IM works today. It’s a big mess.”