As of changeset 7cadcb the HEAD release of HiveDB requires Java6 (1.6). We were trying to maintain compatibility with both Java5 and Java6 but were unable to do so due to changes in the DataSource interface.
We have changed our default connection pooling implementation from DBCP to C3P0. C3P0 has better failure characteristics and we think it will make HiveDB more stable and more fault tolerant. However, it also forces us to update HiveBasicDataSource in such a way that it breaks Java5 compatibility.