How hard is it to transfer owners for a company that is Doing Business As?

Your question boils down to whether you can appropriate the trade name of another business without the owners' consent under circumstances where the name is about to be abandoned. The answer is "maybe" and involves complex questions of intellectual property law, as well as possible issues of creditors' rights. It is important to remember that, even if the name is not s you say, "registered," someone owns it, and common-law trademark rights will apply to it. If the name has commercial value, the owners of the business, not you, are entitled to capitalize on that value. Accordingly, you should consult with an attorney regarding the speciifc facts of this question.