The code for AOL's ubiquitous Instant Messenger, which has more than 50 percent market share, has been opened up to developers, who will now be able to create plug-ins, mash-ups and various applications, writes Forbes.com. The move comes in the wake of recent advances by the competing IM offerings by Google, Yahoo and Microsoft, all of which together roughly match AIM's market share.

Red Herring, which says the developer program is the largest among the top three IM providers, reports that the software developer kit will result in new IM products that "expand its reach and relevance," according to AOL.

Developers may sell their software creations and earn money from ads placed on them, but AOL has set limits and terms, including compulsory licensing deals when products become "too" profitable. Also, no version of AIM will be allowed to connect to users of competing instant-messaging systems or used within corporations for corporate communication.