"Note: If the relevant parameter name space has conventions about associating parameter names with those who create them, a parameter name could incorporate the organization's name or primary domain name"

"4. SHOULD identify a convention to allow local or implementation-specific extensions, and reserve delimeters for such uses as needed."

As has been mentioned by another commenter[0] these parts invite the drawing of parallels to CSS vendor prefixes.

e.g. -moz-/-ms-/etc...

[0] http://news.ycombinator.com/item?id=3540150