Cerulean Studios is readying patches for Trillian to thwart moves by Microsoft and Yahoo to lock the popular instant messaging (IM) client out of their IM networks.

Microsoft and Yahoo both recently said they are planning updates to their IM services that will likely lock out third-party IM clients.

Microsoft is planning its update on October 15, while Yahoo set September 24 as the date.

Microsoft has said it is upgrading the MSN Messenger service because of a security issue, but also said it did not want third-party clients using its network without a form of compensation.

Yahoo said it was upgrading to prevent spammers from hacking into its protocol and sending its users unsolicited messages.

But Trillian is not letting its users be disconnected by updates from the side of Microsoft and Yahoo. Patches for Trillian versions 0.74 and 1.0 will be released shortly, Cerulean Studios co-founder and head developer, Scott Werndorfer, said.

"The patches will be out before the deadlines, and will include both Yahoo and Microsoft updates," he said.

Trillian Pro 2.0, released last week, is already updated.

Trillian had about 940,000 users in the US in July, making it the most popular third-party IM client, according to market researcher ComScore Media Metrix.

Trillian and other clients such as Imici and Odigo allow users to consolidate multiple IM accounts in one client.

Cerulean Studios' patching plan recalls the IM battles of 1999. At that time, Microsoft, Odigo and others were in a compatibility battle with IM leader, America Online (AOL). The smaller players repeatedly made their clients work with AOL's Instant Messenger and AOL would lock out the competition by updating its protocol.

Microsoft's would not comment on Trillian's actions, but said it stood by its process to not allow unauthorised clients on its network.

Yahoo was unable to provide comment in time.