Then you should already know that RAD offers license and royalty free source releases for the 3rd party game tools prior to 1999. Which is the only licensed 3rd party tool that was used by blizzard at the time for their development.
A source license does not allow the licensee to redistribute source code. If differs from a traditional binary license in that you get the source code so you can fix things or change things and redistribute your own binary. A source license is the only sane way to use a 3rd party library.