The Library Creator exports a monolithic VST Sound file that contains samples, presets, scripts and the macro page.
These VST Sound archives can then be loaded in (or better registered to) any other HALion 6 system. If you build your macro pages with the right dimensions, you will be also be able to create instrument libraries that can be loaded in HALion Sonic 3 and HALion Sonic SE 3. HALion Sonic SE 3 will be available for download free of charge on the Steinberg website. To answer you questions: You will be able create a HALion library that can be used in HALion 6, HALion Sonic 3 and HALion Sonic SE 3, but since HALion Sonic SE 3 is free, it can be loaded as a plug-in in any VST, AU and AAX host, and there will be a standalone version, it is not really a closed system.