I’ve recently been on the lookout for Welsh-English dictionaries for Kindle bookreaders (not the Kindle Fire which is a tablet). I’d been hoping that there might be a version of Ap Geiriduron adopted for that sort of Kindle (I don’t think there is, but I’m making enquiries in the background).
However, on my search I came across this:
Note that it’s all legally free and legal under Creative Commons license: BY-NC-SA.
I hope that’s useful to someone.
(There is also a legit free German-English Kindle dictionary available on the web. PM me if interested or just google).