I just put up Mac Client 5.5b20. You can just download the mail file if all you want to do is upgrade your existing setup or you can download the TF5.5b20Headgap.sea if you want the whole enchilada.
Changes in 5.5b20:
Added support for background notification when a chat window receives a new message.
Minor change to Zmodem to improve its reliability if it has trouble starting the transfer.
Changes in 5.5b19:
Old instant message windows are gone, in favor of chat room like windows. This makes using instant messaging much more elegant, providing a way to have a private chat with a user. We're looking for feedback on the new design. You can even assign voices for people you chat with frequently and have your Mac playback the "chat" live.
Added support for Auto GIFs at logon (watch for this feature soon!)
Changed sysop chat window so that it doesn't move to the front when a sysop message comes in.
Fixed a bug where incoming messages from the Sysop chat window could change the background color in other windows.
