Hi,
after playing Doom I & II on the PS3, which supports splitscreen in Co-op mode for Couchdoomers, I discovered this awesome source port with splitscreen support. Great work ! It works very well here (Debian Stretch), even though using gamepads is not straight forward, but unfortunately it seems that the splitscreen is only horizontally available. The PS3 Doom I/II uses vertical splitscreen, which is imho the better choice for Doom, especially for high rooms and areas (advanced not doom-native look up/down feature doesn't compensate the difficult visibility conditions).
So long
LastCoder