it is possible. for example: https://www.inaturalist.org/observations?license=cc-by-nc or https://www.inaturalist.org/observations?licensed=true.
there’s not a user interface in the website to select this sort of filter, but there are lots of filters like this that can be applied via the URL. here’s the specific part of a larger series of threads on filtering via URL that deals with license filter parameters: https://forum.inaturalist.org/t/how-to-use-inaturalists-search-urls-wiki-part-2/18792#heading--licenses (also replicated at https://www.inaturalist.org/pages/search+urls#licenses).
it currently says that license and licensed don’t work, but they actually do based on my testing in the Explore and Identify pages.