I'm guessing:
FAT32 patents. Most Android devices use this partition format (at least for
microSD cards) so they must pay Microsoft patent royalties or use an open
format instead such as ext2 and supply drivers for Windows and Mac which they
probably won't do as it won't work out of the box and Google requires FAT
format if you want access to their market. FAT16 can also be used, but is
limited to 4 GB so it won't work on large microSD cards.
As shipped out of the box, the shared storage MUST be mounted with the FAT
filesystem. It is illustrative to consider two common examples. If a device
implementation includes an SD card slot to satisfy the shared storage
requirement, a FAT-formatted SD card 2GB in size or larger MUST be included
with the device as sold to users, and MUST be mounted by default.
Alternatively, if a device implementation uses internal fixed storage to
satisfy this requirement, that storage MUST be 2GB in size or larger,
formatted as FAT, and mounted on /sdcard (or /sdcard MUST be a symbolic link
to the physical location if it is mounted elsewhere.)
Source: source.android.com/compatibility/2.2/android-2.2-cdd.pdf
Exchange patents. Android cannot provide full support for Exchange without
paying Microsoft. Evolution does (at least partially) support Exchange, so
I'm guessing it is possible to provide partial support by reverse engineering
(or maybe Novell obtained specifications via their agreement with Microsoft).
