I've used it it before, its called Rug Backing. Its the same stuff as slip latex with more ammonia added to it. I've used it in a pinch and it worked ok but you wont save any money using it and I found it drys about the same as slip latex.
Alot of craft stores carry it, its for brushing on the bottom of rugs so they won't slip when you walk on them, they must not sell alot of this stuff because its always in the discount area that i've seen.
Carpet latex comes in outdoor and indoor flavors. Sticks to everything. Plan on throwing everything you use away. Usually takes overnight to dry. I used it last year. The crap drove me crazy last year but, I am a rookie. I now have 10 gallons of mask latex in my garage.