My intention is to know the number of non-free packages installed on my system. In Debian I can use 'vrms' . I think Arch has nothing similar, but I can start programming an application like 'vrms' (maybe using libalpm or calling pacman directly).
My first test has been typing:
$ pacman -Q | pacman -Qi | less
and reading carefully the license fields: most (BSDs and MITs specially) say 'custom'. The big problem I've found is that, quite often, I read the word 'none' there, but I can't understant how can it happen in packages stored in official repos. There are a lot of packages without license field.
I could do a heavy research to know which packages include a license field and which don't, and then warn their mantainers. But it would be a waste of time.