Since the Zaurus is a linux-based PDA, soon after its arrival on the market the opensource community started to customize the installation which lead to the developement of alternative ROMs/distros. Today there are three major linux-based ROMs for the Zaurus besides the original from Sharp: Cacko, pdaXrom and OpenZaurus. On this page I will try to give an overview over the major alternative Zaurus ROMs. Please note: This is not meant as a neutral comparison, all things written here represent my own opinion. You are free to agree or disagree with it.
Cacko is basically an enhanced Sharp-ROM, fixing lots of the shortcomings and adding new functionality. Also it is completely translated to English. The core components are still QTopia and kernel 2.4.20, which enables you to use most of the old apps written for older Zaurus models.
The kernel, besides being the same version as Sharps original is heavily customized an enhanced, adding lots of drivers (e.g. many WLAN, BlueTooth and Ethernet devices for USB or CF) along with various new filesystems supported (squashfs, hfs, ntfs..).
A lot of work has been done in the section of Networking/Bluetooth, so many devices work out of the box. Also WPA support is there and can be enabled relatively easy (see Networking page for details)
Cacko exists in 2 flavors, Cacko Full and Cacko Lite. Cacko Full is similar to Sharps standard ROM, bringing along a set of default applications like PIM, Browser, Office and so on. Cacko Lite is just the bare ROM, installing only the necessary things leaving out most apps and additional kernel-modules (they can be installed later using the cacko-feed). This gives you the choice which apps you want and which not.
pdaXrom follows a totally different approach. Essentially it converts your Zaurus into a mini-laptop by installing an X server enabling you to run a lot of the “normal” linux programs from desktop-distributions. The downside of this is that none of the original apps will work.
Another thing a bit problematic with this approach is, most of the apps are not optimized for an embedded environment, e.g. to get a decent browser you have to use FireFox but knowing how resourcehungry FF is on a desktop its easy to imagine how well (or not) it will run on 64MB of RAM (loading time ~3min..).
Seeing all that one should not forget that pdaXrom still is beta software, which means it has lots of bugs and is lacking features.
Openzaurus is the third of the three major Zaurus distros. There are two main flavors, OPIE and GPE. OPIE is similar to the original SharpROM/Cacko being an opensource implementation of QTopia. GPE on the other hand is X-based and therefor more similar to pdaXrom in the basic concept. Both can be installed and run in parallel with a little hacking. There is also a “bootstrap” variant, basically being the kernel, some basic libs and a Terminal, which is only interesting for developers.
The current versions of OpenZaurus ar build around 2.6.x kernels, thus making them incompatible with the original SharpROM. Also this means that some of the Hardware Features may not work as expected, cause drivers are still in developement.
At the moment there is also a lack of some essential programs. OPIE for example lacks a decent Browser as well as office applications. I haven't tested GPE so I can't say much about it
So after the short introduction of all three major alternative ROMs, which one is the best? For me the answer is quiet clearly Cacko. Its optimized for the embedded environment, supports all Hardware-features and in most cases “Just works”. Also you have access to a really large collection of Software.
Said that, pdaXrom and OpenZaurus do have some advantages over Cacko, but at least at the moment also lack some essential features or have more noticable bugs. In the end anyone has to decide for one self which ROM fits ones needs best.
This is by no means a complete comparison or in-depht test of the ROMs. It only shows my impression of the three ROMS at the moment (December 2006). I only installed both OpenZaurus and pdaXrom for a few days before flashing back to Cacko. Also this is not intented to be neutral, but my own Opinion. A more in-depht comparision can also be found on Meanies Page.