A TclOO question

Hello out there ,
I found XOTclLight (https://github.com/xdobry/xotcl-light ) which is
an XOTcl compatible implementation via TclOO. My hope was that with it
XOTcl's mysterious error messages would be traceable since the calls
wouldn't be buried in XOTcl's binary.
Alas, it errored out with
may not change classes into an instance of themselves
on the line
oo::objdefine Class class Class

While this intuitively makes sense I wonder:
1) Maybe TclOO's syntax has changed since then (2015)? After all, a
man who knows enough about OO systems to implement one in terms of the
other isn't likely to release a package which is evidently unusable.
2) What does the statement cited above try to achieve? And, most
important, what magic can achieve it?

I figured that it attempted to replace the XOTcl command 'Class' with
its own definition so I changed in the script and the call above
'Class'  to 'NewClass' - but to no avail.

Any idea or help will be greatly appreciated
Helmut