There's a DLL somewhere to add a servercmd interface to this, but for a quick solution you can pull up cheat engine on blockland.exe and XOR out the player typemask bit in sServerCollisionContactMask. This should give the desired effect of players 'phasing' through eachother but things like vehicles, bullets, etc. will still collide.
The current address of that contact mask is at 0x71AA6C, so just start cheat engine on blockland and add that address, and modify the value to be (<that value> XOR $TypeMasks::PlayerObjectType). Example: 127000624 XOR 16384 = 126984240.
An interesting thing to note about this is that it breaks client sided prediction that deals with colliding with other players. This can be solved by fixing the mask on each client in a similar fashion (client collision mask address = 0x71AA70) but that requires everyone to participate on their end, so in the end it's a small sacrifice you'll just have to deal with.
