I think there should still be a small fee, so not just anyone can grab a cat for free, though if they can make sure the owners are good, then it is a good thing for the cats! I would get one, but mum got rid of our last one and I still haven't got over it :/
But yeah, remember everyone, don't get a cat unless you are prepared for 10+ years of buying food, vet bills, litterbox cleaning and being careful around doors if it is an indoor only cat, having to deal with injuries or bringing dead animals in the house if it is outside and inside (or dying animals. A cat we had years ago was inside/outside one brought in a crow that was still very much alive and struggling). Though they can also make great pets, and are less matnence then say, a dog in most cases
I was unsure of this as well when I first saw it, especially since it's coming up to Christmas where people may think a 'free' cat would make a nice chrissy present.
Though I trust the people on this forum know better than that and would only take advantage of this offer if they were 100% committed on getting a cat.
Cats have a much lower adoption rate than dogs, and since it is is kitten season there are a lot more cats in the pound, and a lot more being put down. So this is the RSPCA'S strategy to try and save as many of them from being put down as possible. I don't completely agree with it...but honestly I think this makes a cats chances of living a long and fulfilling life much higher.
It's good for anyone who was thinking of getting a cat anyway, and if it encourages someone to adopt rather than buy from a breeder or pet shop etc. then that's great

Also it means more money for you to spend on toys, beds, food etc. for your fury friend.