1) That seems like a lot of work for a plugin that’s supposed to have this option. Better to inform people before they buy, IMHO.
2) I see. I took out any locking and tried the link, and it is indeed preventing the download, so this works.
3) cache dir is writable
Anyway, since I wasted more than a day on this I decided to skip the locking. Maybe it’s for the better, at least wpdm gives me a statistic on how many poeple downloaded the files. Thanks