Why you SHOULD NOT want a device with 3rd party drivers:
Sometimes a manufacturer forks v4l-dvb all on their own and writes a driver for their device so they can claim Linux support. That's great and all, but sadly, you will sooner or later end up in tears.
Sometimes there is another v4l-dvb fork, think multiproto, em28xx-new or s2-liplianin. These either get merged into v4l-dvb or are eventually forgotten. Sometimes a user has written a patch for a particular device, but the patch for whatever reason is not incorporated in v4l-dvb. And sometimes the manufacturer creates their own closed-source driver, like nVidia does for graphics chips or Sundtek in the scope of this wiki.
Whatever the cause, all these are not part of v4l-dvb. Sooner or later the user or manufacturer will stop supporting these, but the Linux kernel will move on. When that happens, you have a few options:
1. Stick with your current kernel for ever and ever. Not recommended.
2. Create and submit a patch for v4l-dvb to support the device that does get incorporated in v4l-dvb. Unless you're a programmer, you may not be able to.
3. Hire someone else to do that. May be expensive.
4. Buy a new device. Oh, you probably shouldn't have bought this one in the first place.
You can contact the Linux-Media Mailing List (LMML) and see if perhaps there is a developer who would be willing to borrow your device to create support for it. No guarantees though.
In the end, you should (sadly) generally not buy these.