Whether consumers will benefit from the confrontation is up in the air, however.
This morning, a Tribal Voice spokeswoman said the company had reconnected its client AT&T's I M Here service with AOL Instant Messenger (AIM) after AOL blocked service last night. The response was the second round in an escalating war over compatibility between the two products and recalls a similar exchange earlier this year between AOL and Microsoft's MSN Messenger service.
In that earlier battle, Microsoft issued three separate versions of MSN Messenger before admitting defeat last month.
Tribal Voice spokeswoman Lisa Wheeler said the company had not made any decisions about how far it would go to provide I M Here users access to AIM users without AOL's permission.
"With each step we will evaluate it," she said. "We have to take it one step at a time."
AOL has failed to respond to repeated requests for comment on Tribal Voice's activities this week. In the past, the company has called unauthorized efforts to access its user lists "hacking."
Although AOL has published its protocol to allow third-party developers to create interoperable products, it has steadfastly defended its right to limit access to its computer systems, where information about AIM users is stored.
Tribal Voice refused to discuss this week's software fixes in detail. Asked whether I M Here makes use of AOL's computer systems in allowing communications between the two services, Tribal Voice product manager Beth Nagengast said, "It uses them similar to the way an AIM client would using the protocols AOL published on their site."
In first denying service to I M Here users on Wednesday, AOL used a technique that disconnected registration of unauthorized users from AIM, according to Wheeler. Late last night, the company offered a different approach, allowing registration but making the AIM buddy list unavailable to I M Here users.
Wheeler would not comment on whether AOL had the right to deny unauthorized users access to its computers.
It was unclear how many variations on the theme might be played out before one side runs out of options, if ever. Unless Tribal Voice can offer a permanent solution, consumers signing up for AT&T's I M Here service face the frustrating prospect of downloading frequent new releases of the software to maintain access to friends on AOL's AIM service.
Instant messaging, made popular by AOL, allows users to communicate with friends and family in a real-time chat format. AOL has dominated the niche by maintaining 45 million screen names in its AIM "Buddy List" network and an additional 40 million registrations in ICQ, the instant messaging software it acquired last year.
Like any networked technology, instant messaging becomes increasingly valuable as the number of users grows, leading some to predict that the advent of a universal standard is all but unstoppable.
"Consumers don't like to be forced" to use a product, Rob Enderle, an analyst with Giga Information Group, said in an interview earlier this week. "And this looks a lot like forcing."
The Internet Engineering Task Force (IETF) has convened a working group aimed at creating standards that would allow friends and colleagues to easily know when and where they are connected to the Internet so they can exchange messages instantly.
Vijay Saraswat, co-chairman of the IETF working group on Instant Messaging Presence Protocol, said AOL executives contacted the group and attended a standards meeting in San Francisco this fall. But he said he has not been able to identify any AOL participants in working group online discussions, where most of the hard-core development issues will likely be hashed out.
"We would welcome their participation," said Saraswat, who also works at AT&T Labs. "It would be a tremendous benefit."
With its enormous lead, however, analysts said that AOL could buck any move toward standards that it doesn't approve.
"AOL owns instant messaging," said Seamus McAteer, an analyst from Jupiter Communications. "Interoperability is inevitable if [AOL] says it is. Don't bet on AOL rolling over."
In July, AOL convened its own advisory group for creating instant messaging standards. Formed at the height of AOL's dispute with Microsoft over instant messaging, the group attracted some of Microsoft's most bitter foes, including industry heavyweights such Bill Joy from Sun Microsystems and Rob Glaser from RealNetworks. Other allies to AOL included Josef "Yossi" Vardi, from AOL's ICQ team, and Novell chief executive Eric Schmidt.
AOL's cooperation in connecting AIM to rival services has been selective. So far, AOL has signed agreements with Apple, Lycos, TV Guide, IBM, RealNetworks, EarthLink, MindSpring, Juno and Novell to develop and launch co-branded versions of AIM, according to a recent statement.
Interestingly, the company has not allowed its own ICQ to connect with AIM.
In addition to Microsoft, AOL has long said it would exclude Tribal Voice and, by extension, Tribal Voice clients such as AT&T. Since this fall, AOL has said it would not cooperate with Tribal Voice, which serves about 8 million instant messenger clients with its PowWow software.
"Tribal Voice, Microsoft et al are using AOL server resources to ride the coattails of a proprietary service that AOL devised and implemented," McAteer said. "AOL was savvy enough to buy the only other contender, Mirabilis [which created ICQ], before someone else snapped it up.
"Instant messaging is not a standards-based service, and AIM customers are not clamoring for interoperability," he continued. "If they do, and I doubt that they will, then AOL should open its service up. Until that happens, others should pay to play."
If AOL is unwilling to hand over access to the AIM buddy list for free, it may be willing to cut deals for interoperability.
According to Tribal Voice, AOL has agreed to sit down early next year to seek ways to end their escalating IM battle.
It was unclear what AOL might seek in negotiations with Tribal Voice, but it could involve collecting charges for access to its list or the right to run ads on Tribal Voice's system.