I saw the message and thought it was an exceptionally poor idea to make an alert about this. I really do not mind adding pirate english language as an option, but I hate getting spammed by software.
Anyway, I accidentally clicked the install button (my touchpad kind of sucks), which gave me the Win7 UAC control dialog. Not interested in installing anything, I denied access. That resulted in Avast crashing. I restarted my computer and now Avast will not start, crashing with the error "Failed to load language dll [1909\UILangRes.dll]".
So this little stunt wasted my time and left my computer without protection. No, Im not installing Avast again. The developers obviously do not consider Avast to be security critical software. Just make software that does what it should, do not compromise security/stability with alerts about pirate english... actually, for any software, never ever make popups for non-critical information, that is basically adware territory.