AOL is opening up its code base, enabling developers to expand its online service, but is holding back on allowing for any convergence between AIM and rival messaging clients and services.

The internet service provider has launched the Open AIM initiative that provides access to AOL's proprietary protocols through a Software Development Kit (SDK). This allows developers to build plug-ins and customised communication clients running on the AOL network.

AOL said Open AIM will "make it easier than ever to connect with anyone and everyone on the web". As long, that is, as anyone and everyone happens to be on AOL's network.

Developers won't be able to build a multi-headed client or bring AIM into another public IM network. AIM chief architect Justin Uberti told The Reg: "You are not permitted to take something and have it log into our network and the Microsoft or Yahoo! network. This is focused around the existing AIM network."

The goal, instead, is to ensure AOL achieves deeper market saturation as developers build new services on the network or plug in AIM to other sites and services. Examples include Pepsi building its own branded IM client, or for buddy lists to be built into the American Idol website so friends can see when you are online.

Uberti said: "We want to come up with compelling new experiences for users. We know we don't have all the ideas. If we give [developers] the tool kits they can come up with stuff in a number of ways. If we have the biggest reach and the most interesting content, that will position the AIM network as a more interesting proposition for customers."

AOL's SDK targets desktop developers using C++ and Java. However, Uberti said AOL plans to support more languages. ®