It's almost impossible today to imagine a time when a Broadway play would have been shut down for obscenity, especially about the long-since-accepted topic of homosexuality. But Paula Vogel's play Indecent, which just opened at the Cort, reminds us in jolting ways that this was a hard-and-fast reality not many decades ago. You need travel back less than 100 years, to 1923, to find a once-prominent, now-forgotten example in Sholem Asch's The God of Vengeance, which combined Jewish tradition with forbidden love of the lesbian kind to result in a production that was not allowed to stay open for long. And in her work, which she created with Rebecca Taichman (who also directs), Vogel explores the ins, outs, and copious changes that affected Asch's play and those who experienced it from the stage, the wings, and, by extension, the audience. . . .