I would think writing from scratch, using the source code as a "pool of knowlege". This way you will get a cleaner implementation and not too much baggage from the platform the source code was targeted for.
Oh, btw, is there an windows-explorer type native program for OS4? If not that might be my port of call, assuming there are services to get file list/attributes/rename/copy etc. Oh and gui elements like multi-column list boxes.
[edit] since explorer is very handy for file management, compared to multiple windows IMHO. [/edit]
PS: Does it matter if my computer is not in the bedroom? :-D