Perhaps I am one of the "cloth-eared" ones. To me, there is enough difference between Christina MacPherson's tune and that of Craigielea to justify calling her the composer. I guess that this argument could go on and on. I base my argument on the original score for "Waltzing Matilda" as published here: MacPherson score

Now compare this with the music for the "Queensland version" at the Univ. Queensland site, which seems to be the sheet music published in 1903: Queensland score

Alan of Australia posted the midi file for Craigielea, 29 Jan 98 in thread 3857. Chords and lyrics are also given: Craigielea

Now the Cowan score is different from both of those given above. Alan gives the midi, etc. in the same 3857 thread.
Here is the sheet music from the Univ. Queensland site: Cowan

OK, since like Clarke I have "cloth ears" I am going to turn tail and let the Aussies argue it out (retire to position of interested unaligned observer, behind barricade).

Since my typing and computer skills are rudimentary, here are the three links as I read them:
http://www.anu.edu.au/people/Roger.Clarke/WM/Score.html (Original score).
Queensland vers.: http://www.uq.edu.au/~mlwham/banjo/waltzing_matilda.html
Cowan vers.: http://www.uq.edu.au/~mlwham/banjo/waltzing_matilda_2.html