The homepage for the project is:
The last version is 1.7
Feb 26, 2008 - Sim390 version 1.7 Version 1.7 of Sim390 is now available for download. It has improvements to the user interface, a new HTML help file, support for changing the font in local 3270 sessions, better and more complete emulation of floating-point instructions, and a minor bug fix for the IPM instruction.
Sadly the author of this program, Dave Edwards, has passed away. There will not be any source release of the emulator, nor will there be any further versions, or enhancements. The same goes for MUSIC/SP.