I read somewhere that if you make your own sound synthesis, then it will not be plagiarism, who knows?
somewhere on their website, I read some kind of agreement, look Marketplace Terms and Conditions
it is better to discuss some specific example
I guess plagiat and copyright infringement is different things, but very close. The first one may not bring you to court , but still will have not pleasant consequences for artist …this is simple stay true, do original things, get inspired by others, and create your own! my advice