-> (e.g. the output of a GPLed program is not GPLed, so why should executing a program on a 3D printer be any different?)
The output of a GPL program (a compiler for example) might not be governed by the license on the program, but might be governed by the license on the source file (the design). I can't take Open Source code, compile it with a GPL compiler and sell it for profit without including the source and attribution because "the output of a GPLed program is not GPLed".
I can't use the IBM logo for my own personal use because I 2D printed it myself. Manufacturing does not wash away any need to respect I.P. rights.