OJDK is GPL v2, so you're a-okay there unless you're shipping a binary (in which case, upon customer request, the source + derivative code has to be released). RH puts out a "100% free" version under the moniker 'Iced Tea', if you want to play it safe. Realistically, attorneys are expensive -- going after a startup worth maybe 10MM on paper for a license violation isn't an economically prudent move for anyone.