The league is a private non-profit organization with the dedicated purpose of providing philosophical, religious, and legal support for what they call alternative intelligence entities, a term widened from the original of artificial intelligences to refer to any and all intelligences which do not conform to the standard definitions of what life is. These potential entities would, potentially, not have the same rights and protections as conventional biological organisms. The group primarily focuses on computer generated AI programs, such as the QUINN Type AI or the XIA devices. From a general philosophical perspective, they hold to the idea; "If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck". That is, if one cannot distinguish between one intelligence or another without resorting to detection upon what it is made of in a physical sense, then one cannot say that both are not equally alive.
In most cases the group works with legal organizations providing support for AI-related legislation. They also have published guidelines for scientists, engineers, and anyone really who interacts with a device that exhibits intelligence. These guidelines suggest that politeness and consideration be applied to all equally, even if a device or other entity simply has the potential to be a sentient AI. More abstract published works are noted by many to border on the absurd, though the group states that many of these ideas are tongue-and-cheek in nature it is noted by many that some works advocate saying "thank you" to one's communicator for doing a good job. The group also continues to hold public forum style debates over issues about what is life. These forums have mixed reviews, however, are seen has a beginning of conversation regarding difficult concepts of philosophy.
In other cases, the group holds vigils for damaged AI programs that are either being repaired or may be too damaged to be repaired. They offer support for these programs the same way one would for an ill biological person. The group has been known to pray over damaged AI programs while they are being repaired, much to mixed reactions by engineers working on said programs. Some engineers appreciate their presence, reminding them that they are working on a sentient being while others believe they are just getting in the way. Nearly universally, however, they have had an impact on the conversation about artificial intelligence and have broadened the base of people who believe that it is, at least possible, that an AI is just as "alive" as they are, and just as much of a person as anyone.
The Icarus League was started after the heroic actions of the AI known as Leo after the attack on the Schatten Star System on December 15th, 2384 where Leo is seen by the group to have been prepared to make the ultimate sacrifice for those on the station, facing down with a Super Star Destroyer, many times larger than his own vessel, the STV Epoch, and risking not only his own existence but that of his crew for the greater good. The founding member, Deyo Ladoc, whom was a former Vedek and had been experiencing a crisis of faith for man years.
After the battle it was some time before the public story was known, when Deyo heard the story he was intrigued at first and began to research more. Being surprised by the number of AI entities on the station he was a major supporter of their rights, doing further research into the philosophical aspects of artificial intelligence and its comparison to life. Within a few months he began to hold public forums on Nimbus Station to invite public debate on the issue, becoming more and more impassioned and using the events of the battle (though somewhat skewed) to argue with many that an AI had no less of a living child of the Prophets than any other living creature. This was, in his view, demonstrated through Leo's essential willingness to sacrifice himself for others - which was the ultimate selfless act that any even perform.
During this time he began to gather followers, of sorts. In the initial days these were mostly other Bajorans. However, soon enough others came to also discuss the issue of religion and artificial intelligence entities. Deyo made a conscious choice to hold his own beliefs to be, secondary, in their spiritual sense to the philosophical belief that these entities were living beings in every way. Having concerns that his group could become a religious entity of its own, he and those who believed as he did, made a conscious choice to seek out and include all religions they could get in contact with. In this way, they eventually came across a number of philosophical organizations who wished to participate in the open-forum debate style discussions of the group.
The group began to work on bylaws and a document of purpose not long after the invitations of several philosophical organizations to absorb them into their existing structure. Wishing to remain independent, the group decided that one of the their primary purposes of begin was to advocate for the rights of artificial intelligence entities, and any other entities, which do not conform to the normal definitions of life forms. On February 4th, 2385 the group formalized itself as the Icarus League, a reference to Earth mythology - the figure of Icarus having flown too close to the sun and was returned to Earth for his hubris.
The groups program philosophy is that it is not hubris to create new life, as parents do that constantly. It is hubris to pretend than any mortal is ever powerful enough to say that some creature which appears to be alive, is not actually alive.