Licence of validation icons?

I have released some WWW-pages under free (in the sense of freedom)
licences for documentation.

For example this one is under Design Science Licence:

http://www.cc.jyu.fi/~juhtolv/runot/

This one is under GNU Free Documentation Licence:

http://www.cc.jyu.fi/~juhtolv/mswordmail.html

Stylesheets are dual-licenced: You can use either DSL or FDL.

Here are homepages of those licences:

http://www.gnu.org/copyleft/fdl.html
http://www.dsl.org/copyleft/

But what is the licence of those icons I get from your validators? Can I
incorporate them to my WWW-pages that are under DSL or FDL or any other
free documentation licence? Here is one example of such icons:

http://www.w3.org/Icons/valid-xhtml11

I guess there are and will be many other persons who want to create free
WWW-pages that are valid HTML. It would be really nice, if they could
use your validator icons without legal risk.


-- 
Juhapekka "naula" Tolvanen * University of Jyväskylä * juhtolv@st.jyu.fi
http://www.cc.jyu.fi/~juhtolv/index.html * * "STRAIGHT BUT NOT NARROW!!"
"Yksin talon pimeydessä istuu valtaistuimellaan lapsi silmin
lasittunein. Itkee sähkön valtamereen."                              CMX