This article is from the of the muppets FAQ, by Craig Silverstein with numerous contributions by others.
Yes, pretty much. Here's how ownership breaks down, along with the date the relevant company acquired control:
o Sesame Workshop: Sesame Street Muppets (Dec 2000)
o Disney: All other Muppets, Bear in the Big Blue House (Feb 2004)
o Henson family: Everything else, including the Creature Shop, Fraggle Rock, movies like Labyrinth, the Hoobs, etc (May 2003)
Before February 2000, the Henson company was independent. In February 2000, the German company EM.TV bought the Muppets. They turned around and sold the rights to the Sesame Street characters to Sesame Workshop (formerly Children's Television Network). EM.TV proceeded to utterly collapse, and in May 2003 sold the Muppets back to the Henson family, for about the value they bought it. Henson then sold the rights to the Muppets (and Bear in the Big Blue House) to Disney in February 2004.
It's interesting to compare the various press releases as the Henson family lost, gained, and again gave up control: http://www.henson.com/company/press/html/022100.html http://www.henson.com/company/press/html/050703.html http://www.henson.com/company/press/html/021704.html
Disney worked with the Hensons before buying them in 2004. As far back as 1989, the Walt Disney Company entered into negotiations to acquire The Jim Henson Company (then Jim Henson Productions) and the Muppets. Jim Henson died during the negotiations, and the deal eventually fell through. However, the JHC and Disney continnued to work together, such as for the (wonderful) MuppetVision 3-D at Disney/MGM studios in Orlando and at Disney's California Adventure in Anaheim. Presumably, we'll now see even more along these lines.