The wording in the original article seemed to imply turning over the source was required by the LGPL, but if I understand what you're saying (You can still request a copy of the source of that library though) it should be more of a "pretty please, if you're feeling generous".
IANAL but AFAIK, the license absolutely does require them to provide the source code for any LGPL libraries that they used. It does not affect/infect their other source code, as would be the case with the full GPL. However, voice.ai was foolish enough to include a GPLv3 component in their product, so all of their source code arguably has been affected by its terms.
The user has to be given a practical way to change the LGPLed code in any way he wants.
They have to provide a way to rebuild VoiceAILib.dll with a modified version of LGPLed library, or just link the LGPL licensed library into it's own dll and don't bundle it with their own code into the same dll.
Providing the full source code for the whole dll is also a way to satisfy the LGPL's license requirements, of course.
The wording in the original article seemed to imply turning over the source was required by the LGPL, but if I understand what you're saying (You can still request a copy of the source of that library though) it should be more of a "pretty please, if you're feeling generous".