MSN and AIM were not open or public APIs AOL / ICQ's proprietary Protocol (ICQ moved to it after being acquired by AOL): https://en.wikipedia.org/wiki/OSCAR_pr

MSN and AIM were not open or public APIs AOL / ICQ's proprietary Protocol (ICQ moved to it after being acquired by AOL): https://en.wikipedia.org/wiki/OSCAR_protocol https://en.wikipedia.org/wiki/OSCAR_protocol I don't really care to look up the details of MSN, but at the time Microsoft was not "open" friendly by any means.