The links you provided mark the officially supported platfroms that our QA team runs the tests and we support for the Commercial and Comunity release, it has nothing to do with licenses. In that chart "no mark" means "not tested".
As a rule of thumb if is supported in the comercial release will work with no issues on community and as it says there any Relational DB that has a JDBC 2.1 driver + SQL-92 compliant; will work for reporting.
Even if is close to that YMMV a lot of people are using Jaspersoft with some odd quasi-relational DB with no/minor problems.
As you see we do not QA datasources (i.e. databases you report on) for the community release since there is no support provided by Jaspersoft. Just this forums and the community, but that does not mean they do not work with CE
Short answer you are good with Oracle (as long as you have an oracle license :)