I think what is meant here is that a protocol dissector code might actually be derived from (read: distilled from) the actual proprietary protocol implementation, and this internal business is the one a company may want to protect. One solution is to provide dissector code which does not rely upon (read: and therefore hides) the protocol implementation, which of course inevitably results in people reinventing the wheel... as is often a company's intention when patenting an idea :^/
Regards, Olivier