I think the correct answer to your question is almost certainly some combination of "it depends on the jurisdiction" and also (in many cases) "nobody can be entirely sure because no court has considered the issue yet"
There have been a handful of court decisions on what "non-commercial" use means – the Creative Commons legal case database records [0] records three cases involving non-commercial CC licenses in the US, one in Belgium, one in Israel, plus I also know of one in Germany [1] which their database seems to be missing. I don't know if any of them addressed the contra proferentem rule which you mention.
The German and US cases on this topic appear contradictory – from what I understand, the German case assumed that all government use is commercial, interpreting "non-commercial" to basically mean "private home use", whereas two of the US cases (Great Minds v FedEx Office and Great Minds v Office Depot) were about use by commercial entities acting under contract to public school districts, and the holdings of those cases assume that government-operated schools are "non-commercial" (and furthermore, the commercial entities were engaging in "non-commercial" use, even though they were acting commercially, because they were doing so on behalf of a "non-commercial" customer). That said, all these cases have somewhat limited precedential value – the US cases are binding precedent in two federal judicial circuits (2nd and 9th) but have merely persuasive value in the remainder of the US; I don't know what the ultimate outcome of the German case was (Deutschlandradio said they were going to appeal but I don't know if they did and what the outcome was if they did), and German law doesn't view precedent as "binding" in quite the same sense that common law systems do anyway
There have been a handful of court decisions on what "non-commercial" use means – the Creative Commons legal case database records [0] records three cases involving non-commercial CC licenses in the US, one in Belgium, one in Israel, plus I also know of one in Germany [1] which their database seems to be missing. I don't know if any of them addressed the contra proferentem rule which you mention.
The German and US cases on this topic appear contradictory – from what I understand, the German case assumed that all government use is commercial, interpreting "non-commercial" to basically mean "private home use", whereas two of the US cases (Great Minds v FedEx Office and Great Minds v Office Depot) were about use by commercial entities acting under contract to public school districts, and the holdings of those cases assume that government-operated schools are "non-commercial" (and furthermore, the commercial entities were engaging in "non-commercial" use, even though they were acting commercially, because they were doing so on behalf of a "non-commercial" customer). That said, all these cases have somewhat limited precedential value – the US cases are binding precedent in two federal judicial circuits (2nd and 9th) but have merely persuasive value in the remainder of the US; I don't know what the ultimate outcome of the German case was (Deutschlandradio said they were going to appeal but I don't know if they did and what the outcome was if they did), and German law doesn't view precedent as "binding" in quite the same sense that common law systems do anyway
[0] https://legaldb.creativecommons.org/cases/?keywords=&tags%5B...
[1] https://www.techdirt.com/2014/03/27/german-court-says-creati... and if you can read German, here is the actual court judgement: https://netzpolitik.org/wp-upload/OLG-K%C3%B6ln-CC-NC-Entsch...