It is 3 isolation transformers etc with a common neutral, so if you wire the Black leg to L1, the Red leg to L2 and your White neutral to N, (and E to the protective Ground), you’ll have the two line voltages available and you can treat each leg and 120 V circuits on both legs identically.
(I believe at the moment, each 3-phase one is final-assembled by hand, so if you ask The Shop nicely, you might get a N.America 2-inputs only version.)
For a 240 V load (if you go that far) you use a single c.t. and tell it to use both voltages. The line in the sketch would look like:
EmonLibDB_set_pInput(4, 1, 2); which says c.t. input 4 will use voltages 1 & 2.
For a 120 V load:
EmonLibDB_set_pInput(5, 1); which says c.t. input 5 will use voltage 1.
All this is fully documented, along with example sketches, in the emonLibDB library zip download. EmonLibDB - Version 1.0.0