That's exactly what is says- "won't work on anything but 2.6.х".
I have no idea what you are using DAQs for, but maybe for Linux you'd like to try MCC devices. They generally have better drivers, they declare support for a wide range of linuxes and in their latest drivers they have some examples for Android. Also, their devices are cheaper, which is not insignificant- if you want to use a cheaper OS, you are likely to prefer cheaper DAQs, too. As far as HW is concerned- same low quality. I think most boards are assembled in the same factory in Hungary.
I could try to run a MCC device in Linux, if this will be useful for you.
You are right and I see on MCC web that they provide better Linux support, but now I don't have any project where I could try there devices, but I'm interested for how it works under Linux.
In my case, choice of using Linux, based on fact that it generally more stable and secured.
Old kernel is not big problem for now, because RHEL 6 and there clones Cent OS 6, Scientific Linux 6 will be supported until year 2020. And I think the newest RHEL7 also supported by National Instruments.
The main problem is the difference between NIDAQmxBase and NIDAQmx. Generally, Windows is supported better.