No, they aren't the same thing. "Food grade" is a regulated term while "non toxic" is basically unregulated. Because "food grade" is regulated it also doesn't make much sense to pay for the testing and verification required to make it conform to those standards when it isn't supposed to be eaten.

Non toxic is more or less a much lesser version of food grade, but really, its not the same. It means that there are no known toxins in it, but it hasn't been treated, packaged, or intended as food at all. As such things like resistance to growing bacteria/mold on it aren't taken into account. There's also not really any regulation around what constitutes non-toxic.

Basically while you probably don't have to call poison control for your kid munching on play-doh, you also probably don't have to call them if they eat a spoonful of dirt.

It's not a good idea at all to let them do it, and can lead to digestive problems, but it also isn't like they ate like... Windex or something which would need immediate medical care.

Everything above is correct, however...

According to Prop 65, the state of California would like you to know that Play-Doh contains substances known to cause cancer. They'd also like you to know that that food grade hamburger contains substances that cause cancer. That the water you drink contains substances that cause cancer. Et omnia alia...

At least if it was crayons you know the kid will be a Marine.

Food grade means it can be safely consumed.

Non toxic means you don't have to call poison control, but it isn't necessarily recommended for safe consumption. 99,999 times out of 100,000 your kid will be fine, but depending on what surfaces that play-doh sat on it could be contaminated with a pathogen that might cause an upset stomach/vomiting/diarrhea. So like any other day of your kid putting random stuff in his mouth, basically.

The air we breath has substances known to cause cancer. That gives it the flavor.

No, "non toxic" is not the same as "food grade". Play-doh is not meant to be eaten, so I would discourage your child from munching on it.

No, "non toxic" and "food grade" are not the same. Eating play-doh is definitely not a good idea and can be dangerous.

Non toxic: You should not eat this, but the ingredients won't poison you at the amounts present in this item.

Food grade: Meets FDA standards for use in making food intended for people. May not be safe to eat the entire container. Food grade dye is safe when used as the instructions show. Eating an entire container of it may make you sick.

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My grill cleaner at work is non-toxic, but it would certainly still give you the runs if you drank it

Mmmm. Forbidden air.

That's my criticism of prop 65. It requires labels for anything that has a IARC category higher than 3 from my understanding and ignores dosage or any other factor. As a result, it's usefulness to the consumer is about zero.