On Friday evening, the small park between Shelton Avenue, the Farmington Canal Trail, and Hazel Street bloomed into a small arts festival that warmed the cool evening with an explosion of color, sound, and good conversation. It was the beginning of the Artspace-organized Open Source Festival’s weekend of making visual art appear across New Haven, not only from downtown, Westville, and East Rock, but from Newhallville and Dixwell to the Hill and Mill River.