Transferring to PUSD from OUSD for Kindergarten

No, you don't lose your OUSD spot if you apply for an interdistrict transfer--in fact, transfer applications aren't even processed until later in the spring, so you likely won't hear back until after you are assigned to an OUSD school. (I also imagine PUSD won't know if they have spots until after their own enrollment process runs.) However, you mention that you don't have any familial connection to Piedmont--to meet the transfer requirements for elementary, you need to either work full-time in Piedmont or have your child care provider (whether that's family or a daycare that continues to school-age) located in Piedmont. The Alameda County Office of Education now processes interdistrict transfer applications for all of the school districts in the county, so you would apply to them. The OUSD website has information on which documents you need to submit to verify that you meet the transfer requirements.

The response you received is inaccurate. All school districts in Alameda County must the transfer application form created by the Alameda County Office of Education. The application is submitted to your district of residence along with any required supporting documents. If approved, the application is submitted to Piedmont (PUSD) for consideration. Per an agreement between all school districts in Alameda County, today was the first day applications could be submitted for the 2o24-25 school year. Check PUSD’s non-resident transfer page for information on their process and how applications are prioritized. The current policy gives priority to PUSD employees and City of Piedmont government employees, but no others.
If you have any questions after reading the page, contact Sylvia Eggert in the Superintendent’s Office at 510-594-2614.  I hope this helps.

It's worth clarifying that the previous responses to this question are talking about two different things: the criteria for being released from OUSD (for elementary, a parent must work in Piedmont or the family's childcare must be based in Piedmont) and the process that PUSD uses to determine which of the students who have been released from their home districts will then be accepted into PUSD (applying criteria that prioritizes groups like children of city employees and grandchildren of Piedmont residents over other applicants). You must first meet the criteria to be released from OUSD through the interdistrict transfer process before the PUSD priorities come into play. At that point, if there are more approved transfer applicants than spots, the priorities for which students get those seats kick in--release from your home district doesn't guarantee acceptance into your preferred district. The OUSD website outlines the requirements for being released from OUSD, and the PUSD website outlines the priorities for accepting transfers into the district. The Alameda County Office of Education now manages the application process for all districts within the county, so you would start there.

Since we just went through this process, I'll add that we did hear back pretty quickly from OUSD once we submitted our transfer request. The next step is to forward the signed form to Piedmont Unified. It was unclear if that would happen automatically, so I did it "just in case" following these instructions on PUSD site: https://www.piedmont.k12.ca.us/about/enrolling/transfers
Last step is to wait for PUSD to make their decision -- as others mentioned, it might not be for a while so you'll need to accept your OUSD assignment in the meantime.