Do you consider it as weird if I thank the open-source community in the acknowledgement section of a paper?
I also mentioned technical forums and Q&A sites (about GAMS, C++, the GNU Scientific Library, LaTeX, Maths, Statistics..., in my case) in the acknowledgement section of my PhD memoir.
I do not really think that doing the same in the acknowledgement section of a paper is inappropriate. As long as it is expressed in the same terms as other acknowledgements, I actually think it is a good and revolutionary idea.
Of course, all the coauthors of the paper should agree in including that kind of acknowledgement, just as it would/should be regarding other acknowledgements.
UPDATE
To expand and complete my answer, I should say that, in my humble opinion,
- the 'Acknowledgements' section of a paper is not usually mandatory;
- in case there is one, it should be kept not too long;
- you can mention anyone or any 'entity' you are thankful to;
- if there are too many people or 'entities' to mention, try to select the most relevant ones;
- you may consider to keep some place for sort of formulaic or routine acknowledgements such as thanking anonymous reviewers, etc.
But, of course, there should definitely be a place for the 'real' acknowledgements. If you are really thankful for the help from online communities, or you just want to highlight it, I think there is no problem. For me, it makes no difference with other 'personal' acknowledgements, such as thanking some concrete colleagues for reviewing a draft of your paper, for instance.
People have thanked thrash metal bands, porn actors, and transportation authorities in their acknowledgments; some have written "unacknowledgements".
There is much more leeway for personal quirks in this section than in any other part of your publication, and it's the least likely to be read.
Thanking someone who actually facilitated your work is not at all weird. It's in fact very appropriate, even if that someone is a collective entity.