require searches $" for loaded features when deciding whether to load them or not. However it does this with a case-sensitive search, and on case-insensitive filesystems the search might fail if two requires use different casing (or if internal file path processing changes case, such as C: to c. It should be modified to treat loaded features on case-insensitive filesystems with case-insensitive searching.
I'm committing an initial fix for this that assumes if jruby home is on a case-insensitive filesystem, all loaded features searches should be done case-insensitively. This is not adequate since jruby may be installed on a case-sensitive filesystem and libraries loaded from a case-insensitive filesystem, or vice versa. It really needs to be done on a feature-by-feature basis. This may or may not be possible.