Britney Spears will share 50/50 custody with Kevin Federline at least through the end of the year, according to TMZ.com. The gossip website says that an L.A. County Superior Court judge extended a temporary custody order that was initially put in place for Spears’s Circus concert tour which started in March 2009. The tour ends in Australia on November 29, 2009.

Apparently, under the terms of the order, Spears is allowed take their two young sons, Sean and Jayden, on the road with her. She must, however, provide Federline with a place to stay if he wants to follow them on tour. The paparazzi has photographed Federline and his girlfriend on several of the tour stops, including some in Europe.

TMZ says that the order provides Spears with minimum 50/50 custody of the kids and, at times, she has even more than 50/50 time. At the end of the year, after the tour ends, the judge will reevaluate custody. TMZ‘s sources say that it seems likely that the 50/50 split will be continued after the end of the tour.

Spears pays Federline $20,000 a month in child support. In addition to this sum, he gets between $20,000 and $25,000 a month when the kids are outside of California. My guess is that this additional money is technically to cover the travel and meal expenses he incurs to spend time with the boys during the tour (and maybe even to compensate him for potential loss of income that he may give up in order to be with them). The amount is pretty high, especially if Spears is paying for his hotel costs (and I’m not sure exactly what income he may lose by traveling), so it likely also represents the result of a hard-fought negotiation.

I don’t believe that the custody order has been changed with regard to legal custody of the kids yet. The 50/50 split refers to physical custody or parenting time. As far as I know, Federline still has sole legal custody as Spears is technically under conservatorship of her father, following last year’s mental and emotional problems.

Until the probate court lifts the conservatorship, in effect finding that Spears is capable of handling her own legal and financial matters, I don’t see the family court giving her legal custody of her children. But we’ve been hearing that the conservatorship will be terminated after the tour ends, so the stars may be aligning for a major legal shift for Spears at the end of the year.