Documentation - Reference to MSDN?

[Max TenEyck Woodbury]

I've been reading the Wine code and noticed that some of the external 
interfaces are practically undocumented. I did a web search on some of 
the names and found descriptions in MSDN.

I realize that copying the information from MSDN directly into the code 
is a poor idea  (like copyright violation) so I have a couple of questions:

1) Would including the URL of the MSDN article be useful/a good idea?

2) Would enumerating coded values and flags be allowed?

3) Where should data structures be documented?