I think this can be relatively easily accomplished by editing the
SCHEMA.XML file stored here:
C:\Program Files\Common Files\Microsoft Shared\web server
extensions\60\TEMPLATE\1033\SPSPERS\LISTS\DOCLIB
Remove any reference to the Upload feature.
You may also want to consider removing the New Document capabilities
too. That is in effect an upload.
There will also be a view with the Multiple Documents Upload link, so
look for that too.
However, when you are all done, people will still be able to use Windows
Explorer to copy files from the file system using DAV. Of course, you
could completely remove the document library list template from the
SPSPERS\XML\ONET.XML file.