Thanks for the interesting questions and replies regarding the phrase "play judo."
I realize the rules of the past did not allow such useage. My opinion is that this phrase (as well as "play karate" et cetera) is now transitioning into accepted and standard English because of its wide useage. A simple network search using the phrase "play judo" can yield many examples. I.e., "TEHRAN, Iran

--Iranian judo champion Arash Miresmaili has withdrawn from the Olympics after refusing to PLAY against an Israeli opponent..." Also, from the same, "I refused to PLAY against an Israeli rival to..."
A new book is titled "Play the Game: Judo - Dando". Rensselaer Judo Club of Troy, New York has "Play Judo. Have fun" on their website. Hollesley Judo Kai of Woodbridge, Suffolk, England begins their websight text with: "Play judo with Hollesley Judo Club"
"Hollesley Judo Club was formed in 1993 by Julie and Neil Jolliffe, both Dan grade judo PLAYers." Lastly, from sportspark.co.uk from Norwich: "Judo is PLAYed within the purpose built Martial Arts Room. Norwich Premier Judo Club is based at the Sportspark and offer..."
With many people and Nations using this phrase, I think it is working its way into acceptance and we don't need to stand hard and fast against "play Judo."
I'm interested in any advice, corrections or comments regarding my view on this.
Thank you for this informative sight and opportunity to learn and grow together.