Would this be a compulsary measure for your clients, to connect to the www via this proxy?

Well i would guess, that because you are running the proxy server then you would be responsible for securing the server so that an unauthorised person could not compromise it!

Again if the user does not have to connect via the proxy then you are not liable, as this was the users choice to use the proxy!

Thats my opinion on this, but by no means am i up to speed on the legalities of this...

Cheers

r3b00+