Yes, it is a hacked client, that's the entire point, when people accuse others on servers of "hacking" what they're actually using is a hacked client which gives them access to things that you normally can't do like kill aura, speed, etc. on most servers these are disallowed because they give you an unfair advantage but 2b2t is an anarchy server so they let you. To install a hacked client you need a purchased copy of minecraft and many require minecraft forge as well (such as the impact client), hacked clients aren't standalone free versions of the game, you're probably thinking of cracked minecraft in that regard.
If you have already installed it i dont see how else they should take personal info. There is another client that I used to use called reflex, but as I started the client it asked for my minecraft password even though it did not need the password, so I knew it was a scam. Clients that ask for password ingame should be avoided, but impact does not I have been using it for 5 days now and it does work and if you want to play on servers then there is an anti it feature that avoids anti cheat. The staff can still ban you though but all in all it’s the best free client that I have ever used. I would recommend it to lots of Minecraft players looking for a way to cheat.