I would going to ask the people that run it if they didn't mind me doing wild releases into their stock, just dropping a book there every now and then. I don't think they'll mind as it's just another book for them to raise funds with...
The other thing I had thought, and which is why I'm here asking, as I was thinking of maybe making it an official Zone to get more books coming in for donation etc. but I didn't know that the feeling was about it here. They don't "sell" the books as such, just ask for a donation. It's out in the reception so you could just take a book if you wanted, but people are encouraged to put money in a collecting box if they take a book.
Is there a rule that says a Zone has to be for free, or would it be okay to have a Zone where we encourage people to wild release, and if they want to catch a book we say that we'd like them to make a donation.
It's for palliative care/cancer so definitely a very worthy cause!
If you think making it an official Zone isn't appropriate then I can always just release there, but I did think it'd be a nice way of getting more book donations.