Items copied from CD as read only
One way would be to copy the files from the command line using rsync: It supports a flag --chmod, so you can say, e.g.,

rsync -a --chmod=u+w /Volumes/name-of-the-CD/ /wherever/


to turn on writable flag for the user (you). Beware, though, that rsync takes a while getting used to, especially when recursively copying directories. Whether or not you end the name of the source directory with a slash actually makes a difference …