1) download and unzip your favorite drupal theme
2) cut and paste the content of page.php into
http://www.web2py.com/php
3) retrieve the generated web2py code and save it as layout.html (this
is not 100% fool proof but works 90% of the times)
4) move layout.html into yourapp/views/layout.html
5) move all the other files under yourapp/static
6) try the index page and you may get some errors...
7) edit yourapp/views/layout.html
and fix the links to the static files and delete any {{...}} that does
not make sense.
To save the theme:
cd yourapp
tar zcvf mytheme.theme.w2py views/layout.html static/styles.css static/
images/*