Talking to bunnyboy, he had no intentions of porting nesasm3 to Linux. So I took care of it and uploaded it. He's going to add it to the repository on his site, but in the mean time, here it is: http://programmingace.com/nesasm3/nesasm3.zip
That package contains the windows and linux binaries along with the source. You're on your own for the OSX version.
That package contains the windows and linux binaries along with the source. You're on your own for the OSX version.