Lately the concept ‘digital’ has been widely exploited to convey a generic message of ‘novel’: we should not fall in this trap.
Moreover, ‘digital’ does not mean ‘discrete’ (a clock whose hands can assume only discrete positions is analog), nor ‘based on electronics’ (several electronic devices are analog), nor ‘related to computer-based online communication’ (digital computers were digital before the Internet).
My current interpretation of what ‘digital’ actually means is presented in the paper “On representing information: a characterization of the analog/digital distinction”, by A.Frigerio, A.Giordani, L.Mari, published in Dialectica, 67, 4, 455–483, 2013, doi:10.1111/1746-8361.12040.
The paper is rather long (in particular it includes a critical analysis of previous positions on the subject) and somewhat technical, but the main thesis is easily presented: a code is a function linking signs and information entities, and the way of defining the code determines whether the representation is analog or digital: if the code function is defined extensionally (i.e., by a list), the representation is digital, whereas if it is defined intensionally (i.e., by a rule), the representation is analog (Section 5 of the paper expands this interpretation, and can be read independently of the rest of the paper).
I do believe that this interpretation is appropriate to explain the critical role of the ‘being digital’ in DiDIY, because through digital (in this sense) coding information is almost completely unconstrained by its physical support and therefore can be easily processed, transferred, stored, etc also by means of simple and very efficient technological tools (say, from the transistor to the Internet of Things).
Being decoupled from its physical support, digitally-coded information not only freely flows and can acquire autonomous individuality (think about computer viruses spreading on the Internet...), but also – and crucially from the viewpoint of our project – can be freely combined with physical systems in the versatile options allowed by ABC (3D scanners and printers, Arduino boards with sensors and actuators, etc).