Just a caveat from a (non-lawyer) lurker: the clean room approach may work
if there are no patents involved (which protect algorithms, unlike
copyright law). However, a previous poster to openafs-devel mentioned
that the license covering the AFS code specifically mentions patents: if
any patents apply to the code you need, I don't think a clean room
implementation will save you. DEFINITELY get legal advice from lawyers
knowledgable in IT IP, and I would ping Prof. Moglen and IBM before I went
anywhere with this.

Good Luck!

Chris Green, MiniBooNE / LANL. Email greenc@fnal.gov
Tel: (630) 840-2167. Fax: (630) 840-3867