if you used something that was defiantly Lucas created. Like R2D2 or Han Solo, Darth Vader Tie Fighter, Millenium Falcon. Yes it is then.
But the concept of a 'lasersword' in sci fi isn't. there are pulp sci fi stories that go back to the 1950s and 60's that have such things. Infact, the concept of a 'sword' that emits energy of one elemental form or another goes back to pre biblical and mythologic times. Sword being a symobol of power, courage, virtue in many cultures, its not surpriseing to find referances in varois mythos of swords combined with the power of the elements ( air, earth, fire, water, darkness, light, good, evil)
even Lucas didn;t call it a lightsaber at first. he called it a laser sword:
(you can read sumations of the original story development here:
http://www.starwarz.com/starkiller/writings/development_brendon.htm)
Same as they can't copyright using the word 'blaster' for a laser pistol, or 'droid' for android ( android and robot are terms that go back to its origins in the Play 'R.U.R.' by Czech playwright Karel Capek in 1920-1921).
editied: BTW if you never read RUR i highly recomend it, you will find MANY sci fi robot stories parallel concepts it introduced. and its probably one of the first recognized modern era Sci fi works
Just don't Call it a lightsaber or use an actual object created by LucasArts.
( BTW th saber hilt in the above IS a LucasArt creation originaly... comes out of Jedi Academy)
