Assuming this is the preamble that they refer to:

When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.


I think it makes perfect sense as a political statement. The idea behind many 3d printed firearms projects is for the public to have access to the tools they need to remain free in the face of a tyrannical government (paraphrasing here, not necessarily expressing my views on the matter)

When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.


I think it makes perfect sense as a political statement when you take into account that the idea behind many 3d printed firearms projects is for the public to have access to the tools they need to remain free in the face of a tyrannical government (paraphrasing here, not necessarily expressing my views on the matter). Regardless of the specific quote from the declaration though, the whole idea of that document is the separation from what was considered a tyrannical government so again, taking into consideration the thoughts and emotions behind this sort of project, it makes perfect sense to quote that over the second amendment.