Here is an 8051 simulator you can use with Unix (and probably Linux):
http://mazsola.iit.uni-miskolc.hu/~drdani/e...ded/ucsim/

According to the readme, it is open-source (GPL), and distributed with sdcc. There is a more-limited DOS version as well.

The latest download version is dated 2004. I have run 8051 images on it before (probably loaded as hex or bin files).

From the link above:

µCsim can be used to simulate microcontrollers. It supports MCS51 family. AVR core, Z80, HC08 and XA are supported by UNIX version only.
Download
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Features of the simulator

Code analyzer.
The simulator tries to figure out places of valid instructions in code area. This feature included in both DOS and UNIX versions.
Processor types.
The simulator can simulate different type of microcontrollers.
Multiple consoles.
The simulator can handle more than one command consoles and accepts command from multiple sources. It also can be driven by other programs such as debugger interfaces.
Serial interfaces.
The simulator can virtually connect a terminal to serial interface of the simulated CPU.
Memory simulation.
Simulated CPU provides address spaces, storage is simulated by memory chips, address decoders conects them together.
Command syntax and command reference. (Now updated up to 0.5.0)
The simulator can be controlled via a command line interface. It accepts simple commands.