Diablo 1 HD Hellfire Mod | Awake

Is this mod playable yet?

Would love to get some multiplayer in some time

Also, will this mod keep spells/arrows hurting your fellow players or allow it to pass harmlessly through them when you haven't purposely gone aggressive on other players?

Can't imagine playing alongside a sorc or a rogue with this mod when they spam spam spam arrows/spells like they do in higher level areas.

Is this mod playable yet?

Yes

This mod is still in alpha version (no quests; bugs; needs balances) but it's playable since 0.091 (that's when I started) for multiplayer fun.

When someone joins your game or you join others you are automatically in party and can set hostile against player(s) or back to friendly mode (actually I don't remember trying this). Unlike Vanilla Diablo 1 your summons can't be damaged by you.

In the vanilla Diablo 1, even when you were marked as friendly to other players, your stray arrows and spells would still harm/kill them.

Has that been changed?

Yes, it's fixed.