Sorry about this change, but it was intended actually. We had some issues with wrong guild being fetched when for example one guild is called "original" and the other is called "öriginal" so we're now searching for binary match of your request. We might change back to case-insensitive search soon tho, it's just that there's a lot of preparation for cataclysm changes going on at the moment and we're forced to focus on that.
What I did to fix it for my raid attendency software was just do a normal select and then afterwards loop over the results and do a strtolower($guildname) === strtolower($row['guildname']). But I guess you're smart enough to figure out solutions for this yourself
Could you inform me some way or the other when you decide what solution to pick? So that I know what to change as it seems folks actually use the JSONP service I set up (around 100 000 requests in 3 months).