"Before the Play" was published twice (as far as I know): once in 1982 in Whispers, and then again in 1997 in TV Guide. The link above goes to what appears to be a transcription of the TV Guide version, which is an abridged version -- with all the naughty language excised -- of the Whispers version.
So, to answer your question: yes, but not all of it.
It would be neat if SK would include "Before the Play" in a re-issued version of The Shining. Was/is it going to be re-issued since Dr. Sleep is coming out?
Well, he did eventually re-release 'Salem's Lot with the parts that were edited out from the original version. They were put at the end of the book in a seperate section, not placed in the actual story. And, we all found out that 'Barlow' was not the original name of the bad guy! Maybe someday there will be an edition of The Shining with Before The Play put back in.....