STRS, PARS, Pro Bono - this does not make sense

I have found no law restricting the amount of time one can volunteer. No payment, no limitation. I am certainly willing to be corrected.

STRS does not limit volunteering nor pro bono work, only paid work. Cindy says “NO PAYMENT” and “PRO BONO MEANS NO PAYMENT” and “ HE IS DOING IT FOR FREE.”
This is no adding up, can someone explain to me how Allan would be limited to work under STRS if he is working for free. The District does not pays for STRS. The District is paying $180,000 for Allan’s PARS.

From Allan’s email
My PARS Program Participation
When I notified two board members of my intention to retire, they asked whether I would be available to participate in ongoing projects, such as these. To be able to do so, I had the choice to enter the PARS program or to work within the limitations of STRS.
If I chose STRS, I would be severely limited in the number of days I could work in retirement. PARS allows me to work the days needed, at a financial savings to the district. This point is key as program participants must 1) demonstrate a cost savings to the district, as well as 2) receive approval from the union and the district. For me, PARS does not add to my retirement, nor allow me ‘early’ retirement; it only allows me to work more days as a consultant than I would be allowed under STRS.

From Cindy’s Email:
DISTRICT IS NOT PAYING ALAN GORDON TO WORK. HE IS DOING IT FOR FREE.
ONCE AGAIN, THERE IS NO CONTRACT, NO PAYMENT TO ALAN GORDON.
ALAN GORDO0N IS DOING THIS TO GIVE BACK TO OUR DISTRICT. HE IS COMMITTED TO OUR DISTRICT AND WANTS TO SEE CONTINUED SUCCESS.