You have bared this Potential Datasources:
Potential Datasources#Bundesamt für geographische Dienste WMS (BGDI WMS)
and saying that the license is unclear.
On this page  they talk about OpenSource award, and a set of freely usable data. Did you ask swiss topo (for example at email@example.com) to clarify the status of the license ?
CU and thanks in advance Stéphane Brunner Sarge 14:55, 25 October 2010 (BST)