I could never say for sure that a driver(kext) that works in an old version of Mac OS X will work in El Capitan, however...
let me long-windedly explain what that means(sorry @bloomk, greek time):
a kext is a kernel extension, the kernel being the software that talks to a computer's hardware, and the extension being the software that tells the kernel about a specific type of hardware (eg. usb wireless sticks).
most third party hardware companies provide their kernel extension as a pkg, or package file to make it simple for you to put the kext where the kernel sees it(it most likely installs to /System/Library/Extensions on old Mac OS X, or to /Library/Extensions for El Capitan). Some of these pkg "installers" will also install apps to /Applications, such as the wireless utility that edimax uses. the problem is that the pkg sometimes will fail or not install correctly if the version of Mac is not what it was intended for...
to find out if this failure is superficial or if the driver/kext really is not compatible, we have to move these files into place manually with a tool like Pacifist, then reboot and hope it worked. to verify, remember the name of the kext file you see in Pacifist and open About this Mac > System Report, scroll to the bottom and select Extensions, wait an eternity for the list to show up, then see that your kext file is in the list, and is loaded. if so, you win. you should be able to launch the wireless utility and it should function as expected
if telling Pacifist to "install to default location" doesn't work, you're still not finished. you can use Pacifist to install the kext manually to /Library/Extensions(which seems to be where they want 3rd party kexts in El Capitan- Apple must have taken a hint from the hackintosh community to separate Apple and non Apple kexts), and to install the wireless utility app to wherever you want. if after reboot it still doesn't work, then you can be extra sure its incompatible by running the steps I mentioned above where you extract the kext to the desktop and use the terminal to set permissions and manually load it. if the kext doesn't load, then I believe we've exhausted our options and must wait for the hardware vendor to give us a new driver
...so the bottom line: if the kext for any device is compatible with El Capitan, but the pkg installer from the vendor is not, then most likely all of these methods will allow you to use your device (eg. wireless card, tv tuner, sound card, usb nerf missle launcher, pci devices, you name it) 🙂
good luck with your hacks! if you get your device working, please post back with the type of card and which approach worked
