One of them has other organizers, but I don't believe anyone changed the
status. The other one has only me. I'll watch to see if it happens again.
Why would a course that is closed for sign-up still allow signups (even
if it isn't archived)? We generally close courses for sign up when they
are "complete," but leave them unarchived for a while for participants
who are lagging and want to continue to work.
That's probably it. There is a chance that "open for sign ups"
had more to do with it being placed in the listings page than it
had to do with actual sign-up function being on or off. Dirk can
test and confirm and we can probably review functionality and make
some quick fixes.