The no mains power ethos is avoid things (and that generally is limited to music creation gadgets) that require Alternating Current and so can be run without it i.e. with no mains power. That means internal or external batteries (with a little bit of cheating). The exception to this is a PA system if playing live.
Read more: no mains powerThe other main thing is that whilst there will be links to cool gadgets that NMP finds useful, all these have been purchased rather than gifted. And in the unlikely event that offers of free gear are received, they will be declined. Regardless of what people say, a truly honest view can only really come from spending your own money on something (without some sort of tax offset either).