From the 2016 VBB Players FAQ:
Do I need to sign up as a pro?
MPO is the designation for Men Pro Open. For the Birdie Bash, this just means men (as opposed to FPO, which just means women). The Birdie Bash is a fun casual event and we do not anticipate many (if any) true pros signing up. The only reason we used these division designations was so that if a player that has ever cashed in a PDGA event wants to play in a Birdie Bash, then we are required to put them in a pro division. Since there is no cash payout, the division status will have no effect on Ams playing in the division.
From the 2016 VBB Players FAQ:
Do I need to sign up as a pro?
MPO is the designation for Men Pro Open. For the Birdie Bash, this just means men (as opposed to FPO, which just means women). The Birdie Bash is a fun casual event and we do not anticipate many (if any) true pros signing up. The only reason we used these division designations was so that if a player that has ever cashed in a PDGA event wants to play in a Birdie Bash, then we are required to put them in a pro division. Since there is no cash payout, the division status will have no effect on Ams playing in the division.