DVR RDK is entirely user space code so there isn't much effort to port to Android if you already have EZSDK functional. Only posix phtread APIs are used by dvr rdk library code.
From getting a full DVR system functional the main challenges will be:
1. Stable Syslink support on Android. If you already have syslink functional reliabily on Android you should be fine.
2.A huge number of device specific fixes have been done in SATA/USB/EMAC/Nand drivers and are part of the Linux psp used in DVR RDK . You will have to merge in these to the android kernel if they have not already been merged. I don't know enough to know if it is possible to merge these linux device drivers to Android kernel.
3. DVR app (not the dvr_rdk library) uses QT for all GUI . I assume you will use UI from Android and not use QT. If you are using the DVR app then the GUI portion will have to be modified.
4. You will have to port the ti81xxhdmi.ko,vpss.ko and ti81xxfb.ko which are loadable kernel modules used in dvr rdk . Not sure how simple it is.
5. DVR RDK uses the sysfs entries to configure VPSS parameters like display resolution. You will have to enable sysfs support. Not sure if it is enabled by default.
All of above are not specific to DVR RDK but apply to ezSDK as well. If you already have video pipeline using OMX components functional on Android on 814x getting DVR RDK functional will not be a big effort.