It should be a legal obligation that, passed a certain threshold of time and user base, you are required to do so.
HOWEVER, on a slight tanget from that point...If this company and its software have ever received any sort of taxpayer funds, then my opinion is that from the beginning, such software should have been open sourced. Publicly-paid software should be publicly available. Of course, said business has every right to earn profits from providing the service such as hosting said software for convenience for customers. But, every citizen who paid taxes has a right to see (and access!) all the code...well, that's my belief anyway. ;-)