You could ask.
Basically, there are two sketches in use. The one factory-installed on the emonTx is the Continuous Monitoring sketch - EmonTxV3CM, which is designed for the UK single phase domestic supply, but it is suitable also for the N.American single-phase split phase system.
If you have a 3 phase system, either 4-wire or the less common 3-wire, then you must use the 3-phase PLL sketch Update to 3-Phase PLL sketch - #21 by Robert.Wall
That download is the complete sketch and documentation. You should not attempt to use the pre-compiled version that has been put on Github as it is almost certain that you will need to adjust the options that are only available by editing the source code.
If you have a 3-phase supply (see the ‘Learn’ pages for how to identify whether you have), then using the single-phase sketch will not only give you negative powers on phases 2 & 3 (phase 1 being the one that the a.c. adapter is on), but those powers will be roughly half the correct value. If you don’t have the a.c. adapter, it will still be wrong, but less wrong, because it will indicate apparent power using a guessed voltage - the value for phase 1 that was previously correct (the real power) will now be wrong because it’s apparent power using the guessed voltage instead of a measured voltage, but probably by not too much (maybe within 20% if you’re lucky) and the ‘powers’ for phases 2 & 3 will improve but still be wrong by roughly the same amount.