My little pinkie tells me you are a fellow more junior coder and that you are trying to deal with a situation that is not in your full authority (management or HR). I guess you have been talking of it as a team and are trying to bypass the hierarchy because you expect them to potentially fire him. You may be alone thinking of actually doing more than talking about it between yourselves.

This is nice. You seem to care. That is a good point.

Talk to him and listen to him. Nicely, as a friend and ask him how he feels about it. The alcohol is there to alleviate a big pain. The pain will be worse if he tries to stop violently. Violent withdrawal put your body in bad state anyway. He may have tried and experienced it first hand and may be scared to try again. If he does share his experience, it means he has made a lot of work on himself already.

You can propose him attending one AA meeting (together or not). It is a nice beginning because they don't guilt people and they actually know what they talk about.

They will probably confirm HN is not the right place to ask for help, and that my advice were a tad wrong.

AA seems to work for some people. It does not fit others.

If it fails, well, maybe it will still help him begin to do the second step. There are other solutions.

I don't know your proximity. Just don't over-invest yourself and accept you might fail.

Helping him for the first step and talking to him is way more than most people do. So if you fail, don't guilt yourself.