Ah, common names—so wonderfully descriptive, poetic, and unwavering. Wish the same could be said about scientific names. Naming mushrooms, molds, rusts, smuts, and other fungi have always been a systematicist's (scientists who name and categorize new species) nightmare.
Aristotle and 2,000 years later, Carl Linnaeus, who developed the Latin based system of naming species, both classified fungi as plants. It wasn't until the 1960's that the fungi were given their own kingdom separate from plants and animals. But wait! In the 1990's data from DNA sequencing indicated fungi are more closely related to animals than to plants. Additional DNA evidence has now banished the slime molds completely out of the fungus kingdom and into an entirely different group! Neither fungus, plant, nor animal, but protists. Slime molds are more closely related to free living singled celled organisms commonly found in pond water than to mushrooms.
So whatever new designation the mycologists (scientists who study fungi) come up with at their annual meetings, you can rest assured that the scum laid out on the rotting log after a rain will always be called "dog-vomit-slime-mold" by the ranger naturalist.