Hm, yeah I can’t think of any from the top of my head. I guess the site’s format works best for euros and the audience seems to be geared towards that too.

In general, no the site is not open source. There are however some games whose implementation is public under various licenses. A few examples:

https://github.com/AntonioSoler/bga-santorini https://github.com/micahstairs/bga-innovation https://github.com/bga-devs/bga-heat https://github.com/quietmint/bga-hardback https://github.com/bga-devs/bga-memoir https://github.com/Syarwin/bga-kingdombuilder