I now have an Apache2 configuration that seems to do what I want which means that the Fost 4 code, the Boost build scripts and sundry other things (like the PyThai Python User Group files) are available via anonymous HTTP now.
For the Boost build scripts:
svn co http://svn.felspar.com/external/Boost boost
For Fost 4 (best do this in an empty directory as its build scripts will fetch other dependencies into the same directory:
svn co http://svn.felspar.com/public/fost-base/stable fost-base
And for the PyThai files:
svn co http://svn.felspar.com/public/pythai/trunk pythai