It is probably as well for you to be clear about what you are allowed to do with your program. You can check this from your initial MYOB userguide and paperwork. Perhaps the key words are as follows:
MYOB Technology Pty Ltd (the publisher), through its local publishers and distribution agents, hereby grants to you, the original purchaser, a paid up, personal, non-exclusive and non-transferable Licence to use the software and the User Documentation only in the region, territory or country specified on the packaging, or in the United Kingdom and Eire, subject to the terms and conditions of this Agreement
There are no conditions or time limits. The misuse of Digital Rights Management facilities in the software has allowed MYOB to potentially breach its side of this agreement. Nowhere else in the licence is there any agreement or escape for the publisher to withdraw the licence, or render the software unuseable to the buyer.
Clearly the licence is issued by the Australian legal entity, through its selling agents (ie. Mamut). They claim that with the withdrawal of MYOB from the UK market there is no alternative but for the existing users to move to another program. However there is another answer - join the Association and accept our confirmation codes to allow you to continue.