AOL has released partial specs for parts of OSCAR but neglected to include the sections necessary for ICQ compatibility, and there is an obsolete draft RFC for MSNP. Both of those protocols have been reverse engineered and documented fairly well, but there are no open source implementations suitable for use as jabber gateways.
Sorry, but that's just not true. OpenFire has an excellent opensource IM gateway plugin with support for all of the protocols he mentions. The only one still missing from the open source community is Skype.
Is an open source plugin for a specific jabber server (OpenFire) suitable for use as a gateway that works with any jabber server? I wouldn't think so. Plus the OpenFire plugin is a hodgepodge of 3rd party libraries in various states of neglect.
As a matter of fact yes, but with some workarounds. However, let's assume the answer is "of course not" instead: But it can be easily adapted - that's like creating a new filesystem from scratch because ext3 or reiserfs hasn't yet been ported to whatever platform you're working on - and going on to claim that no open source filesystem exists simply because you don't use any of them :)
Sorry, but that's just not true. OpenFire has an excellent opensource IM gateway plugin with support for all of the protocols he mentions. The only one still missing from the open source community is Skype.