When Edward Burns's latest romantic comedy, "Purple Violets," had its premiere at the Tribeca Film Festival in April, it drew positive reviews, but only lukewarm offers from movie distributors...So he and his partners, who spent $4 million making "Purple Violets," instead are gambling any chance of recouping their investment on a distribution deal that involves not a single theater. On Nov. 20 the film will go up for sale exclusively on iTunes. David M. Halbringer reports.