Development Base: The main source the developers use to add functionality and content to the program that is independent of platform (i.e., it is designed for the hardware the developers will be using to make the game).
Port = Modifying, removing and adding code to a development base in order to make code operate on different platforms, or with different hardware.
Parallel = Working on multiple ports at the same time.
You can't compare a 'port' and 'parallel' development since one is a state and one is a development methodology.
GTA V PC is a port. Rockstar PR "dismissed" the port because "port" sounds like a negative term and they want sales, and the build logs prove exactly what I'm saying. The GTA V PC code was the branch for next-gen consoles and PC, and then they had the branches specific for Xbox 360 and PS3, but they all would have shared a development base and the code would have been copied into each branch.
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