from Variety Magazine's Video Business:
...some popular TV series are still being held back from DVD release because of licensing issues. Fox has looked into releasing season sets of Roswell and Ally McBeal, but music licensing costs running into the millions of dollars have held those up, said Peter Staddon, Fox senior VP of marketing.
Both of those shows began production before DVD was an established revenue stream, and music rights for home video weren't cleared.
Unless the DVD will do a big volume, the cost to get music clearance can be prohibitive. Staddon said Fox is still hoping to negotiate a lower cost for music rights for many of its TV shows.
One TV show DVD release that fell through because of music issues was WKRP in Cincinnati.
"We couldn't afford to do it because of a clearance issue," Staddon said.