As far as I can see, you can't lose by participating: they offer free prototyping for the contestants, and there's a prize pool of $1000.
Visiting the site, only slightly embarrassingly, my words welcome you. :D That's because I was asked for my thoughts on DIY keyboards and I also gave the nice people at Seeed some tips with regards of the time frame of the contest and also to make the Seeed Bazaar listing optional.
The rules are quite self-explanatory and clearly explained on the event page.
You have to use one of the five Seeed XIAO controllers: Seeeduino XIAO, Seeed XIAO RP2040, Seeed XIAO BLE, Seeed XIAO BLE Sense or Seeed XIAO ESP32C3.
In exchange, Seeed asks you to review their service and to allow them to share your project on their social media platforms. The design does not need to be open-sourced and production files will not be shared with the public – unless you want to.
In addition, I'll try to keep an eye on this competition and feature some promising projects.