SDL bought the XML Editor Xopus several years back. I think it's been morphed into some other product or maybe sold (or just junked?). My company is still paying SDL for our corporate license, but I find nothing about Xopus on SDL.com anymore.
How can I pick up the trail?
AFAIK, the Xopus browser-based XML editor was never sold separately by SDL, but used as part of what is nowadays known as SDL Tridion Docs (the Structured Content Management product).
In the latest version of SDL Tridion Docs, Xopus has been replaced by a more user-friendly, browser-based XML editor called Fonto
It was morphed into SDL LiveContent back in 2014 I believe. At that point it was called "LiveContent Create" and you can see where it lies in the stack here: https://docs.sdl.com/LiveContent/content/en-US/SDL%20LiveContent%20full%20documentation-v1/GUID-55008675-34AC-45DA-9D19-F2D08A44D3F4
If you search on that site you will see numerous references to Xopus.
EDIT: just seen the previous response from Rick. I can't find anything specific as to where it lies in relation to the Fonto in the stack - but I would certainly check with your SDL Account Manager with regards what you should be working with in terms of version/naming/app! etc.
