Is it legal to use MOD version of any app

i have saving my files to terabox app with a paid subscription recently I found a mod version of this app terabox pro app which is completely free is it legal to use or safe?

Maybe? Maybe not? Not sure how anyone here would know that answer.

Sir, this is a forum for rclone.

First of off, this is not the right place to ask.

Second of all, regardless of legality, would you trust it?