OK Toast is now at 17.3 build 5532. No update available over the update link so it will not selfupdate: http://img.roxio.com/updaters/toast/v173/Toast_Titanium.zip does not work yet.
Only possibility is to download the installer downloader: http://softwareupdates.roxio.com/downloads/toast/17/Toast_17.dmg which will then require a correct serial number and download the 17.3 complete installer into the download folder. Installing that will give you the current version. If you have the Pro version it will download the current Pro installer. This is a bit around the corner thinking, but it works. This version works properly so far with Mojave.