Indian Mujahideen seems to be a pseudonym

'There is no outfit called Indian Mujahideen

With Ahmedabad blasts, we are led to the same foolish theory of Indian Mujahideen(IM). The Indian has claimed responsibility for the Jaipur blasts.
source: May 15 2008: http://www.rediff.com/news/2008/may/15rajblast9.htm

It appears to be clever ploy by the terror groups by invoking the Indian Mujahideen. So it is the third time the name of this lesser known outfit is coming to the forefront. The first time that the country heard of this outfit was during the Uttar Pradesh court blasts in November last year 2007. Then the Jaiput blasts and now the Tsunami serial blasts in Bangalore/Ahmedabad.

http://www.rediff.com/news/2008/may/15rajblast9.htm says Intelligence sources quoting as
The Indian Mujahideen is a creation of the Bangladesh-based Harkat-ul-Jihadi and the rejuvenated banned outfit SIMI.

It was during the interrogations that took place in Karnataka where seven suspected terrorists were arrested did the name Indian Mujahideen figure for the first time. These persons were questioned about the outfit and they reportedly told the police that it was a pseudonym used by SIMI activists to divert the police. It was also revealed that for every person in the force, it was mandatory to have five different names.

Essentially Indian Mujahideen seems to be a pseudonym. This is a relatively new ploy by HuJI and SIMI in order to keep their identity concealed. After the UP blasts, a mail had been sent in the name of Mohammad Shameem, claiming that the Indian Mujahideen had carried out the attack