Is it possible to access the SDK files if you are not sitting in front of a MorphOS machine? Can the sdk.pack file somehow be unpacked without the supplied installer tool?
Certainly. It's a tar.xz file.
With recentish tar (and with xz-utils installed):
tar -Jxf sdk.pack
With old tar (but with xz-utils installed):
tar --use-compress-program=xz -x -f sdk.pack
Or if everything else fails, do it in two steps:
xz --decompress < sdk.pack | tar -xf -
If your system doesn't have xz-utils, you can always build it yourself from the source:
http://tukaani.org/xz/