Sorry for the very late outdated answer. But after read this post, I feel the obligation of give you an answer, not just for answering you, but also for keeping it for historical reasons in SCS-4DJ software info (for curious, hackers, and SCS4DJ fans) before it will get lost forever in the internet.
Officially there's no listing of historical past firmwares on SCS.4DJ support page (http://www.stantondj.com/stanton-controllers-systems/scs4dj.html). However, I discovered that old firmwares are still there (in http://www.stantondj.com/pdf/products/controllers/scs4dj/XXXXXXXXXXXX folder ), but not accessible from the support page (Only accesible via direct URL). These firmware files doesn't have a standard naming convention so obtaining these is not an easy task as just changing the numbers on the URL.
With the help of Internet Wayback Machine, I fetched old versions of the support page (and some more with a bit of creativity with the names) and I was able to obtain almost all (probably I missing some of them) past firmwares. Here:
v5.0.1 (the one that appears actually on the site and since 2014 :( ) http://www.stantondj.com/pdf/products/controllers/scs4dj/SC-IXV5.0.1.zip
And just in case, I made a mirror for the firmwares here too, for historical reasons :D
I'm not much into SCS.4DJ actually, I'm just curious beacuse my brother actually uses it a lot and sometimes told me about their "Linux-based" stuff on it, and helped him updating to 5.0.1 for FLAC support. I know development of this hardware might be abandoned right now and the hardware seems outdated now, but it's still interesting :O :D
Did you know firmware files contains a TAR GZ cabinet? If you're curious take your compression tool, unpack it and have fun :D! For more interesting info about: https://web.archive.org/web/20170919090945/http://blog.switchsystems.co.uk/2012/04/stanton-scs-4dj-under-the-hood/