Arduino is common open source microcontroller platform that is widely accepted among hobbyists and non electronics professionals. However open source doesn’t mean free – if you want to obtain one there are two ways: purchase a readymade board from supplier like Sparkfun or build one as all plans and schematics are freely distributed.
Again why to go through all development process and build exact copy of Arduino board only for some prototyping. You can assemble minimalist Arduino platform on breadboard with few necessary components. Anyway this is only a core Arduino. In order to program you still need an USB to serial FTDI dongle – but this can be separate and not a part of project. Again, this is nothing new and extraordinary as you can always find more Arduino Breadboard projects in the internet.