Aπ' όσα διάβασα (και κατάλαβα) ο αντίστοιχος ελληνικός όρος είναι " η "εμπορική επωνυμία", δηλ. πώς η επιχείρηση είναι γνωστή στους τρίτους.
DBA είναι συνώνυμο του Fictitious Business Name (US English)
Tο αντίστοιχο σε ΗΒ,Αυστραλία : T/a (trading as )

1. DBA
Why do you want one and how do you get one?
A fictitious business name, assumed name, or DBA (short for "doing business as"), referred to as "trading as" in the UK, allows you to legally do business as a particular name at minimal cost, and without having to create an entirely new business entity. You can accept payments, advertise, and otherwise present yourself under that name. In fact, if you present your business under a name other than your proper legal name without proper notification, it may be considered fraud. Fortunately, filing for an assumed name is so easy and inexpensive, there's really not much excuse for not filing one.
http://www.legalzoom.com/dba/index.html
2. DBA (wikipedia)
The phrase "doing business as" (abbreviated DBA or d/b/a) is a legal term, meaning that the name of the business or operation does not include the legal name of its proprietor, the names of all partners, or the official registered name of the limited partnership or corporation that owns it.

In the United Kingdom, Ireland and Australia (and some parts of the United States and Canada), the phrase trading as is used. This is abbreviated to t/a. In several U.S. states, such names are also referred to as trade styles, fictitious business names, or assumed business names.

The distinction between an actual and a "fictitious" name is important because businesses with "fictitious" names give no obvious indication of the entity that is legally responsible for their operation.
'έπεται συνέχεια

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Note added at 2 hrs (2007-08-08 14:42:15 GMT)
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Επίσης η εταιρία ΧΧΧ(εννοειται), ασκούσα εμπορία υπό την επωνυμία ΨΨΨ
Τimas Ltd (ασκούσα εμπορία υπό την επωνυμία Galileo Ireland)
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2...

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Note added at 2 hrs (2007-08-08 14:45:38 GMT)
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Warner Lambert UK Ltd µε την εµπορική επωνυµία. ParkeDavis.
www.emea.europa.eu/pdfs/human/referral/lopid/Lopid Annexes ...



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Note added at 8 hrs (2007-08-08 20:44:15 GMT)
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http://www.dbaform.com/ >>>>>
DBA, short for "doing business as", is a formal declaration that an individual, company or organization is conducting business under a different name. DBA's are also commonly referred to as fictitious business names, assumed business names and trade names. All these terms mean the same thing.

Consequently, , in the US, and under US Law an individual can do business under another name.
If this individual or these individuals is/are not registered as company, business law still apply. This is a guess which sounds logical: a guy presents his self as a company and do business as Guy Ltd. Legally speaking, I suppose he he will be considered as a trader and business law rules shall apply to him.
Same case under under French Law: if an individual acts like a trader, French business law applies to him
In conclusion both a company and one or more individuals can have a fictitious (πλασματικό) name.
Personally, I should translate : Ο κος και η Κα H, ασκούντες εμπορία υπό την ονομασία " Jekyll & Hyde Ltd.".....
Δεν ακούγεται λογικό?

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Note added at 8 hrs (2007-08-08 20:45:08 GMT)
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ή " ασκούντες εμπορία υπό την επωνυμία"