The article describes this as being like a fork. For example, choosing between OpenOffice and LibreOffice, or ffmpeg and libav. Both are the current version, but with different ideas and implementation.
If two groups are editing a book about Python (for example) on a wiki, they might have different ideas about how a particular concept should be explained. They fork that, and both versions can exist in parallel, even exchanging ideas when suitable.
If two groups are editing a book about Python (for example) on a wiki, they might have different ideas about how a particular concept should be explained. They fork that, and both versions can exist in parallel, even exchanging ideas when suitable.