A Planned musical inspired by the tunes of the Spice Girls, “Viva Forever,” is taking forever to develop because members of the ’90s pop group still can’t get along. Judy Craymer, who was behind the mega-musical “Mamma Mia!,” is producing, and Jennifer Saunders, who starred in cult hit “Absolutely Fabulous,” is writing the show, which we’re told would follow a mother who takes her daughter to a talent competition, all set to Spice Girls tunes. But sources say the five original “Wannabe” singers are holding things up: Even though they won’t be in the show, they’re supposed to be giving Saunders feedback and ideas. “Melanie Brown [Scary Spice] and Melanie Chisholm [Sporty Spice] can’t agree on anything,” says a source. “It’s driving Jennifer crazy.” Meanwhile, the former Posh Spice, Victoria Beckham, is busy with her fashion line, and just isn’t as enthusiastic as the rest. The show, which has been scheduled to debut in London by year’s end, has reportedly been delayed before because of the busy former pop stars’ scheduling issues.