Allerca
is now taking orders for hypoallergenic cats
þ NYT. It turns out that no genetic engineering was
required. There's a natural mutation which suppresses production
of the major allergenic protein, Fel d 1, so they were
able to selectively breed for cats with the allele.
This is pretty cool, though pricy: the cats are $3950
with an estimated delivery date of November 2007--plus you
can pay $1950 for expedited delivery.
Since the Fel d 1 suppressing allele is naturally occurring and no genetic engineering rocket science was involved, it should be a straightforward matter for another organization to reproduce the breeding program: all you need is to be able to test for the relevant gene--or the expression of the protein--both of which are well-understood technologies. Lots of people want to have cats and cat allergies are incredibly common, so I'd expect to see other vendors of hypoallergenic cats sometime in the not too distant future.

The folks at Allerca could have patents out (though my brief search has not found any patents assigned to them.)
Allerca sends out its cats already neutered, but presumably others in the business in the future might not do that. I wonder if, in 50 years, the majority of the world's cats will by hypoallergenic because of human selective pressure.