All I can say is don't spend too much time on these sources. I feel that FullPlay (the company releasing this particular library implementation) is being desceptive to not prominently mention that ivdev only decodes vorbis beta4 or earlier files. This is a significant limitation - Ogg Vorbis hit rc1 in June of 2001. So anything encoded since then won't play. Additionally, this code has issues, such as crash bugs. I actually asked John Ripley NOT to add vorbis support with this library - and he agreed it would be bad to have it only play old files, which will sound relatively bad, and fail to play current ones (John, I apologize for speaking for you).
The reason this "integerized decoder" exists is a messy tale. In my opinion FullPlay is just trying to do damage to Xiph.org (the non-profit org who authors Ogg Vorbis). Xiph.org sells their own (CHEAP) arm-capable decoder that plays all Vorbis files, has lower memory usage, etc.
I've told the Empeg folks that xiph.org produces a vorbis lib they could cheaply purchase to add support, and I understand that the suits probably balk at spending any money to add Vorbis support (for now). I know the developers at sonicblue really, really want vorbis support, so I don't mean to imply for a second that they are the problem. However, it is not the case anymore that "there are no integerized decoders available for Vorbis", so don't accept that answer from companies.
I believe that the powers that be will see the need to add Vorbis support to all their products sooner or later, all we can do is keep asking.
Jon