Samuel French pioneered the field of theatrical licensing and publishing in the late 1800's, together with British actor, playwright, and theatrical manager Thomas Hailes Lacy.  Samuel French Inc., bearing the name of it's co-founder, embodies these entrepreneurial ideas of licensing plays and publishing scripts.  Actors perform plays and memorize scripts licensed and published by Samuel French Inc.  Thus, the words of playwrights published in scripts are fondly known by actors as the Samuel French.

 

And all clues point to the fact that Professor Plum killed Colonel Mustard in the conservatory with the lead pipe.