It is indeed really great that libspotify has been released for the arm architecture. From a technical point of view it would be no problem to switch to the official library as openspotify is api compatible; however, the current terns of use does not allow the library to be used on mobile internet devices (and N900 belongs to that category). Florian did post a question about this on the spotify forum, and they responded that they will consider a change to the usage terms. Hope that this clarifies the situation.
#if SPOTIFY_API_VERSION > 4 sp_session_create(&m_config, &m_session); #else sp_session_init(&m_config, &m_session); #endif