Longhorn and Yukon Actually Don't Share That Much Code

“Clearing up some of the mystery surrounding Microsoft's efforts, Sorensen said that products using the storage technology will not have common code, as many industry watchers have thought. Instead, individual product groups within Microsoft will each develop storage systems based on a common design specification.

Yukon and Longhorn "are two completely separate projects--different development teams, different development schedules--so there is no schedule impact. Yukon delays will have no bearing on Longhorn," Sorensen said. "There is a shared philosophy, not so much shared code." [1]

[1] The Long Road to Yukon. http://zdnet.com.com/2100-1104_2-5129900.html