In trademark law, the owner of a mark (Nvidia in the case of CUDA) can usually make someone stop using a mark if it would lead to “consumer confusion about the source of the goods” (i.e. people seeing “CudaText” and assuming it has an association with Nvidia/CUDA).

IANAL, and have no idea how likely Nvidia would be to succeed in a trademark dispute with this developer. But in situations like this, it’s often good to just not use a name if a large section of your target audience could become confused upon hearing it. Even if you didn’t know about the other product when you came up with your name, and even if it’s technically legal.