Leaping, I would allow. Crowhopping, which is something completely different, I would not.
On a crowhop, the pitcher moves the pivot foot forward off of the pitcher's plate, then completes the delivery. She is, essentialy, taking two steps forward instead of one, starting the pitch closer to the batter and gaining extra momentum.
A leap just means that both feet are airbourne at the same time. You can leap without crowhopping (even though most casual observers intermix the two terms and just call it all "crowhopping").
It just seems silly that the exact same pitch can be legal if the pitcher's toe is touching a few molecules of dirt, but illegal if the toe is a fraction of an inch off the ground.
By the way...leaping is already legal for adult male pitchers under all of the major softball associations. But crowhopping is not.
The International Softball Federation (ISF), the governing body for most softball played around the world outside of the U.S. legalized the leap for all ages and genders last year. They still prohibit the crowhop.