Mere moments ago, quoth I:
In the context of Boost.Serialization, this means that you can pass the serialized representations across shared library module boundaries but you cannot pass archives or the serializable objects themselves across those boundaries, unless both shared libraries also use Boost.Serialization itself as a shared library.
To put this a simpler way: If you want to be able to use Boost.Serialization as a static library within shared libraries, then you must make absolutely certain that there are exactly zero #includes or references of any kind to Boost.Serialization's header files in any of the public header files of the shared library. If everything compiles after that, then you should be ok. This usually requires making use of PIMPL techniques.