This problem has been fixed in ClarisWorks 2.1.
Selecting Lock File from the Get Info dialog box does not prevent you from saving changes to a ClarisWorks 2.0 document. You will get warning messages that the file is locked when you open the file, but the file is not read-only as you might expect.
The problem occurs in the French version of ClarisWorks 2.0 as well.