There are several antonyms that would apply to "noncommittal." For instance, certain, decisive, determined, and sure are all antonyms for the word noncommittal.
An antonym (opposite) for certain is maybe not certain
"Well, I suppose," was her noncommittal reply. His response to the job offer was noncommittal.
He was noncommittal when talking about the implied new taxes in the boardroom.
antonym: uncertain, unsure
When the lovestruck boy asked the girl of his dreams to go steady, she was very noncommittal.
Certain.
There is no certain answer to this word.
Yea
Certain and uncertain
(antonym means the opposite of course) "to dislike" is probably the best one "to spurn" would work as an antonym in certain situations.
brittle whittle little spittle
Uncertain, Doubtful, Hesitant, Unsure.