[tex-live] Strange missing resource

[Karl Berry]

    There is, as far as I can tell, no copy of "texbook.tex"
    included.  Is this intentional, 

Yes.

    and if not, would it be possible to add it ?  

No.  As I expect you know, Knuth grants no permission to run
texbook.tex, let alone modify and republish it.

    I would also like to see Victor
    Eijkhout's "TeX by Topic" bundled if at all possible;
    Victor writes that "it’s available under the Gnu Free
    Documentation License", so could it too not be included ?

Yes.  It is already there: texmf-doc/doc/english/texbytopic.