Usually companies don't so this because of legal risks - ie. Some of the libraries they used perhaps they didn't license in a way that allowed opensourcing. A

Usually companies don't so this because of legal risks - ie. Some of the libraries they used perhaps they didn't license in a way that allowed opensourcing. A law change could fix this. Ie. A new antique software preservation law could enable any software be opensourced, yet prevent any lawsuits relating to any actions taken under that law. The law could give extra incentives too, for example requiring that any software ever sold commercially either be archived in perpetuity, or opensourced. Legally archiving something forever is expensive, so many will opt to opensource it.