Not exactly.
There is (or at least has been) also the convention that the top folder
of a tarball has the same name (case-sensitive) as the tarball (without
.tar{,.gz,.bz2}, and probably also dropping the version, starting with
the first dash). So while there's no problem with mIxEdcAsE package
names, they have to be *consistent* on proper filesystems I think.
We for example recently had trouble with Python, in sage-spkg properly
setting up the source folder for building. (Upstream changed from
lower- to uppercase in the folder name IIRC.)
Not sure how robust sage-spkg meanwhile is.
All folders (package names) in build/pkgs/ are lowercase though; and we
obviously shouldn't have *different* packages "foo" and "Foo" or "FOO", say.
-leif