Genealogy.com owns Family Tree Maker and several other genealogy related items including UFT and GenealogyLibrary.com.
Since they are the parent company they have merged the GenealogyLibrary.com sort of with FamilyTreeMaker.com so sometimes you get both of the on the same screen.
Ancestry.com is not related to Genealogy.com as far as I know. They are related to MyFamily.com and other genalogy ventures.
Both Ancestry.com, GenealogyLibrary.com and Genealogy.com are all putting census images on the internet for various prices.
I think GenealogyLibrary.com has several states images for the 1850 census (I do not know if they will ever add more).
Genealogy.com is adding census and seems to be competing with GenealogyLbrary.com so they can charge more for the new images they are adding. (I think this is why GenealogyLibrary.com is stagnemt).
Ancestry.com has some 1790 and other census images online and I think they are adding additional images. They advertise that they will have all available census images online within a year or so. The images here are available at an additional cost above the subscription to Ancestry.com.