I do not have the answer to this! For safety's sake it might be a good idea to take a few precautions.
There are a number of ways to protect the material:
1) The ZIP file may be password-protected. This password must
be stated every time the ZIP file is unpacked.
2) Demanding a user name and a password on the Web page before
being admitted to the rest of the Web pages.
3) Restrict the distribution of news messages and/or establish
mailing lists comprising those persons who may read the newsgroups
in question, for example the NITOL groups.
It is also essential to state copyrights for the author in the
lessons. This makes it somewhat harder for others to use your
material. However, it is also desirable to be liberal in the use
of teaching material. If a colleague or another upper-secondary-school
teacher should want to use your material, this should not be difficult
to arrange.
Nonetheless, if other institutions were to want to utilise the
material commercially, for example for their own courses, that
would put the matter into another light. In such cases agreements
must be entered into before the material is used.
In actual fact we are entering new spheres here. When we offer
our material electronically it is very easy to copy the material
and use it in other contexts. It is even very easy to edit it
or rework it so it becomes more difficult to recognise.