It depends on the terms of the copyright license the author chose, but generally yes you should get permission.
Tbh if I really wanted to translate/adapt/etc something^ and the author doesn't respond to requests for permission, I'd do it anyway under anonymous accounts, include an explicit disclaimer from the very start that I'm not the original creator and it's just a fan translation, and keep ad revenue off.
This is going to work for you until it doesn't. I mean you literally just admitted that you broke copyright law by doing so right off the bat. There is a very good chance they didn't respond to you because they don't want to grant permission, and the easiest way to avoid ambiguity is to not answer. They are entirely in their right to shut you down.
My moral of the story is if it isn't yours, avoid gaining money or reputation from it at all costs so the original creator has no actual reason
This won't protect you. By using their property, you gave them reason enough.
(and stay anonymous in case they're a jerk and decide to do so anyway)
This also isn't going to protect you. Unless you're hiding behind Tor, it's not hard to identify you.
And they're not a jerk, they're protecting their property.
The real moral here is don't try to play lawyer. Unless you're ACTUALLY an IP lawyer, you are not capable of navigating this. Any decision about whether or not you're in the right or wrong for using someone's property is up to a judge in court, not yourself. Always get permission.