Postgresql 8.3 is relational database, compatible with Adempiere 353a/354a (and older version of Adempiere). Postgresql 8.3 vs Oracle XE 10g is in limit of available spaces, oracle have 4gbytes max data. Its too spaces if u not need pictures (for products, for scanned contracts, other documents, files, pictures in jpg, pdf, png and other formats). With Oracle sql developer can be develop very easy Oracle tables/procedures and functions, but plugin for postgresql not exist yet. This is simple examples how can user/users install Adempiere 353/354 with postgresq databases. I was trying it, based on Ubuntu 9.04 operating systems.
Fig 2 creation new database with pgadmin III
Fig 3 Adempiere_pg.dmp will install adempiere relational model with initial data, with utility dumping, like pic 3 descibe
Fig 4 Runing RUN_setup.sh installation begin.