Looked into this the other day, as I too don't use Windows (Linux infact); In short the simplest solution was to setup Windows on a virtual machine and then mount CTX3030's as 'USB Mass Storage Device'.
Click
here to download VirtualBox, it will work for OS-X users also. (assumption: you have a Windows setup disc).
In a little more depth, XChange2 is simply a web-app wrapped in an application container called 'Chromium' (the same core as the Google Chrome browser), it could run on other platforms - if you can work out the parameters to 'build' your own. Windows users can verify this by looking around inside "%AppData%\XChange2".
The firmware on the actual detector, and the XChange2 application appears to access and store settings, modes, and 'other' stuff (like find-points) via a
SQLite database stored in the detectors file-system named 'CTX3030.mlx'. It also attempts to self install firmware images placed in the same directory.
In theory, it's possible to write you're own application to replace XChange2 - this also explains why placing modes directly in the devices file-system doesn't work; the 'mlf' extensioned files are simply database snippets of relevant information that the application imports back into the SQLite database on the device or itself for manipulation.
For me, emulation via VirtualBox was an acceptable solution - emulation via Wine didn't work, and Minelab have done a great job with XChange2 - I don't think I could do any better.