The Polish translation is borked. It should be "lipiec" instead of "lipca" and so on.
There's no animation like with the stock calendar (but it's a minor thing, that's no problem)
There's should be more spacing between the bars which mean the events
Scrolling effect of default calendar is achieved by jumping to previous-or-next month when days outside the current month are clicked, and is greatly missed in Qalendar.
fremangordon and joerg_rw fixed the autobuilder (or rather removed libx11-data and fixed stuff related to extras-devel), you should try uploading qalendar again.