Yes and no.
You cannot do it directly -- IOW you can't just backup the db from UNIX and restore it on Windows and magically be upgraded.
When changing platforms you generally have to dump and load. The fastest method is (usually) a "binary dump". The binary dump format is portable across platforms and upwards compatible. So you should be able to binary dump from UNIX and binary load on Windows.
When changing versions you will also need to recompile. If you have the source that should be fairly easy. Usually it just compiles and off you go. Sometimes there are new keywords that conflict with the code but those are easily dealt with.
Make sure that you use the character client on the Windows side -- compiling UNIX character code in the GUI environment will result in a very unpleasant UI.