Forks can appear for many different reasons even just for testing some pet theory held by a small bunch of devs on the team. As for duplicating effort how about using copy&paste?
Having such similar code-base allows me to use OpenOffice Extensions on LibreOffice. I have heard that they don't all work but most do. LibreOffice appears to have incorporated some Extensions into it's main code-base where a lot of users were keen for it.
As it happens, LibreOffice has apparently allowed several previous forks to re-combine. Ubuntu didn't use OpenOffice but added some modifications and a few changes making it Go-OO rather than OpenOffice proper but Go-OO has now had all it's modifications incorporated into mainstream LibreOffice. Several long out-standing bugs have been cleared up where Sun and Oracle wouldn't push through the code that had been written to solve the issues.
Finally one of the fears that pushed people into creating The Document Foundation to run LibreOffice (as Mozilla runs Firefox and other projects) has happened. It seems that Oracle announced they would drop OpenOffice.
So, forking encourages innovation and competition, collaboration and increases the chances of a project surviving beyond it's owner's whims.
A smart move indeed
Regards from Tom
