I've never seen 不懸 elsewhere, but the list probably lists up items free from quality concern. I have drawn my inference from the meaning of 「懸念なし」.
http://dictionary.goo.ne.jp/leaf/jn2/68670/m0u/

All depends on the style used in the source document, but if that source is:
- exclusively for in-house and informal communication
- the style is telegraphic, condensed/elliptic to save time and/or space
- the phrase appears in a table column with no room to fit much in
Then , would have no qualm in rendering this with the amusing native colour of Japanese-English used by engineers on the shop floor i.e. the above used as an Adj, as in:

Work | Standard |
Surface finish | Don't care |

But if you are not game, then, 'immaterial' would succinctly do the job.


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Note added at 8 days (2015-04-28 10:26:07 GMT)
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I thought I'd never find an instance of this on the Net, but here is one:

"The Prolog variable _ (underscore) is a "don't-care" variable, which will match anything (atom, number, structure, …). For example, the rule...."

http://www.cse.unsw.edu.au/~billw/dictionaries/prolog/dontca...


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Note added at 8 days (2015-04-28 12:47:29 GMT)
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Here are some more instances of 'Don't care' used as Adj or ...Nouns this time.

http://www.allaboutcircuits.com/vol_4/chpt_8/10.html

"Don't care cells in the Karnaugh map'

"These six invalid codes are don't cares as far as we are concerned. That is, we do not care what output our logic circuit produces for these don't cares.

Don't cares in a Karnaugh map, or truth table, may be either 1s or 0s, as long as we don't care what the output is for an input condition we never expect to see.

These instances come from the IT programming field.