The No. 1 rule of premium cable is that you do not give away your programming for free, lest you ruin the whole exclusive feeling you get out of paying extra every month to watch vampire or fantasy epic soap operas. Unless, of course, the prime target for your show is a demographic that by and large does not own teevees, especially not ones with fancy cable machines. So, young, broke, TV-less people of Brooklyn, Girls, Lena Dunhan’s much-hyped show that’s supposed to be about your life is debuting on Sunday. But HBO is making an unusual move and by letting you watch the first episode online for free the day after it airs (along with the pilot of Veep). The show will be available on HBO.com, YouTube, DailyMotion, TV.com, and elsewhere. Perhaps they’re wagering you’ll get so hooked you’ll pay for it after that?