"Identi.ca is similar to existing microblogging sites such as Twitter, Jaiku, or Pownce. Unlike those services, Identi.ca’s underlying software is available under an Open Source license. Identi.ca is also the first service to support OpenMicroBlogging, a standard for exchanging short messages between microblogging sites. Identi.ca also makes public user data available under a Creative Commons license in standard formats."
