It might technically be an offence under the Computer Misuse Act:

http://www.opsi.gov.uk/acts/acts1990/Ukpga_19900018_en_2.htm#mdiv1

...depending on whether the access is "unauthorised". However it is more likely to cause the subscriber to contravene the subscription contract, by allowing somebody other than an employee to have access. Our Action Pack subscription has quite a few restrictions - the software should not even be used outside the company's premises.