AndronЕсли вкратце, то первоначально была СУБД IBM Cloudscape (минианалог DB2, притом написанная на java). Затем IBM что то там пересмотрели с лицензированием Cloudscape, и появилась СУБД Apache Derby, она же JavaDB (поставляется вместе с J2SE6 Mustang). Т.о. все три названия есть суть одной СУБД IBM Cloudscape.
Если точнее, то
Cloudscape Inc, an Oakland, California start-up, was founded in 1996 to develop Java database technology. The first release of the database engine, then called JBMS, was in 1997. Subsequently the product was renamed Cloudscape and releases were made about every six months. In 1999 Informix Software, Inc., acquired Cloudscape, Inc. In 2001 IBM acquired the database assets of Informix Software, including Cloudscape. The database engine was re-branded to IBM Cloudscape and releases continued, mainly focussing on embedded use with IBM's Java products and middleware. In August 2004 IBM contributed the code to the Apache Software Foundation as Derby, an Incubator project sponsored by the Apache DB project (see the Incubator proposal). In July 2005 Derby graduated from the Incubator into the Apache DB project.