For those folks that use pidgin or adium for the OTR encryption feature I can say the current version of the java based client jitsu (https://jitsi.org/) seems to still interoperate with Yahoo.
This of course teaches us why non-centralized open standards based solutions are better. It is a shame that some of us have to interact with clients who do not understand or accept that there are better ways to do things than Yahoo Messaging.
If anyone has figured out what changed on Yahoo's end I am sure the folks at pidgin.im would love the input, even if as of now they are still not admitting there is an issue. Since Jitsu still works I can only guess that the libpurple problem was caused by counting on edge case use, or using something that "worked" but was outside the yahoo spec.