Leap-A is not a trojan, its a worm (of sorts). Some of the AV vendors do have there heads screwed on though:

(taken from Sophos web site www.sophos.com)

Is Leap-A a virus or a Trojan?
Some members of the Apple Macintosh community have claimed that OSX/Leap-A is a Trojan horse, and not a virus or worm, because it requires user interaction (the user has to receive a file via iChat, and manually choose to open and run the file contained inside).

However, this is not the definition of a Trojan horse.

A Trojan horse is a seemingly legitimate computer program that has been intentionally designed to disrupt and damage computer activity. Importantly, Trojan horses do not replicate or have any mechanism of spreading themselves. They have to be deliberately planted on a website, or accidentally shared with another user, or spammed out to email addresses. There is nothing inside a Trojan's code to distribute themselves further to other victims.

Trojan horses do not contain any code to distribute or spread themselves, viruses and worms do.

OSX/Leap-A is programmed to use the iChat instant messaging system to spread itself to other users. As such, it is comparable to an email or instant messaging worm on the Windows platform. Worms are a sub category of the group of malware known as viruses.

Therefore, it is correct to call OSX/Leap-A a virus or a worm. It is not correct to call OSX/Leap-A a Trojan horse.