First of all, this is a very good and useful library. Thanks a lot for the good work!
Secondly, there is a small problem with the declaration of the version in osmpbf.h. Right now it is declared as a const pointer to char. The problem with this is that it is not really a full constant. It should be either:
const char version = "1.2.1";
const char* const version = "1.2.1";
I have problems when I'm including the header in multiple sources.
This is now fixed by making it a macro.