Publishing paper using an open-source software

Yes, it is possible to publish a paper on model analysis. I would treat this like any other situation in which I wanted to use someone else's "data". Generally, it would be the owner of the data (in this case the developer of the model) that would do the analysis. In the absence of an analysis that I need (or want, or think would be interesting), I would contact the owner(s)/developer(s) and see if they have plans for a similar analysis or would like to collaborate.