Sorry for the spam, now my original message seems to have reached the list twice: at first I sent the message without subscribing to the list and when I saw that the message did not reach the mailing list archives, I sent it again after subscribing, but now (two days after sending) the first message also arrived.
I am not sure Thorsten's suggestion of sharing files over SMB (I guess that would mean mounting the share using the cifs filesystem driver or something similar) would make things easier, since the problem of mapping Windows ACLs into POSIX permissions is still there (I haven't tried svn on cifs, though). A simple solution would be just to avoid using a working copy in an NTFS filesystem in Linux. However, in a dual boot system it is sometimes convenient to use an NTFS partition in Linux. As I wrote, this is possible but svn could act a little more nicely in some cases and I guess that would not be very hard to do. However, since there seem to be not many people interested in using svn on NTFS in Linux, and I myself currently don't have time to look into svn's source code as well, the conclusion is only that anyone using svn on an NTFS partition in Linux should keep in mind that one has two choices: a) allow all users full access to the partition and do not use any of the gid, uid, umask, fmask and dmask mount options (e. g. use only the boot option "defaults"), b) set the uid to the user who needs to use svn on NTFS (e. g. use boot options "defaults,uid=1000"). Then other users cannot use svn on that partition (and if they try to do so, and they have write permission, then they will corrupt the working copy's .svn subdirectory). Kind regards, Jaan