Postgres-R has been initiated in the context of the DRAGON project at the ETH Zürich, Switzerland. Bettina Kemme and Gustavo Alonso have written the famous paper Don't be lazy, be consistent, which they published in september 2000 at the International Conference on Very Large Databases in Cairo, Egypt. They proved it is possible to circumvent high deadlock rates and poor response times even in syncronous, multi-master replication systems. They found the perfect basis for their work in Postgres, version 6.4.2 at that time.
The main contributors of this prove of concept were:
Around may 2001 Darren Johnson (firstname.lastname@example.org) and others have started to integrate Postgres-R into Postgres version 7.2. They concentrated on master-slave replication with failover support. Unfortunately that project got stuck and did not keep up with the development of Postgres.
Since 2002 Markus Wanner (email@example.com) has been working on Postgres-R. He again concentrated on multi-master replication and based his work on both previous projects. In July 2006 he presented his work at the 10th Anniversary Summit of Postgres. Two years later, in July 2008 he published up to date patches of a working prototype.