You've worked long and hard to add your vision to the open source project you love, on which you've worked, debated, and to which you've contributed inestimable amounts of code and insight.
But it's not going to work out with the existing developers.
You finally need to fork the code.
How do you do this and remain on the best terms possible with the existing project? How do you not say, "Oh yeah? Fork you!"
Aside from the mechanics of cross-polination and assuming that the reasoning for forking is sound, logical, and acceptable, what issues come up?
Competition? Resource sapping? User poaching?
How do you go through this arguably difficult and long process until you've diversified enough that these are no longer seen as problems?
Rather than discussing the reasoning behind the decision, please assume that you have already been convinced that forking the code is the best overall solution, and now the point is to move forward in the best way possible.