Sam Buss has modified the licence statement in his bussproofs.sty package (to lppl) and we now have the package on ctan (macros/latex/contrib/bussproofs). it will be at the major ctan sites, in its final form, in the near future.
the package allows the construction of proof trees in the style of the sequent calculus and many other proof systems.
users may browse the package via its catalogue entry
http://www.tex.ac.uk/tex-archive/help/Catalogue/entries/bussproofs.html
thanks, sam, for your help in making a readily-distributable ctan package.
Robin Fairbairns
For the CTAN team