==  Giorgio Orsini is Orsini. Please, stop propagating nonsense! == 

 Here are two English language references 

 ↑ A holiday in Umbria: with an account of Urbino and the Cortegiano of Castiglione by Sir Thomas Graham Jackson, J. Murray, 1917, page 38 

 Giorgio Orsini died in 1475, and, so far as I can ascertain, at Sebenico, where he had a house on the doorway of which he carved the bear, the badge of his family, and the mallet and chisels and other implements of his craft2. 
 ... 
 2Illustrated in my Dalmatia, the Quarnero and Istria, vol. i. p. 406. 

 ↑ Delightful Dalmatia by Alice Lee Hornor Moqué; Funk & Wagnalls company, 1914, page 109 

 But alas, only the doorway now remains of the house which "Michelle Simeonich, a nobleman of Sebenico, sold to Giorgio Orsini for two hundred golden ducats of just and good weight", in the month of June and the year 1455. On the lintel of this old doorway is carved a bear, the heraldic emblem of the great house of Orsini - carved, no doubt, by George's own hand, over this door through which he must have passed so often. 

  
 Then from the Italian side: 

 ↑ Per trecentosettantasette anni: la gloria di Venezia nelle testimonianze artistiche della Dalmazia by Giuseppe Maria Pilo, Edizioni della Laguna, 2000, page 37 

 Giorgio di Matteo Dalmata - com'egli si firma - è probabilmente nativo di Zara e certamente veneziano di formazione ancorché molto noto come Giorgio da Sebenico per avervi a lungo operato e avervi creato con la cattedrale di San Giacomo il suo capolavoro, o come Giorgio Orsini, cognome usato dal figlio Paolo dal 1512, ufficialmente dal 1516, e confermato al nipote Giacomo nel 1540 dal governatore... 

  
 ↑ Atti e memorie della Società dalmata di storia patria, Volume 6 Società dalmata di storia patria, La Società, 1969 page 164 

 Ci siamo dilungati un po' a parlare del figlio Paolo per dimostrare che con era poi quella figura "insignificante" come vorrebbe il Fiskovic.  

 Bottom line 
 1) It is quite clear that Giorgio used his family name along with the heraldic emblem of his family 
 2) Italian author Giuseppe Maria Pilo, as a serious historian, tracks the use of Giorgio's family name by his descendants: by his son Paolo and by his grandson Giacomo. This is just in line of the proof that Giorgio belonged to the noble Italian Orsini family, which was formally recognized by a court decision in the year of 1540. 
 3) So, Fiskovic wrote a nonsense, which was refuted in the second Italian reference