No JDK license required for SQLDev. See https://www.oracle.com/java/technologies/javase/jdk-faqs.html
I am a customer of an Oracle Product that uses Java. Does Oracle Java remain free for me?
If you are a customer who has a current support entitlement to any Oracle Product that includes Java, you continue to have free access to any Oracle Java SE updates for use with that Oracle Product. See this My Oracle Support (MOS) document (requires Oracle Support login) for more information.
Thx. I found this FAQ.
Question concerning SQL Developer is that SQL Developer is a free tool so you have no support entitlement. Is Java free in this case?
Any oracle product requiring java is good to go. If you want to get technical, then SQL Developer is included as part of your Oracle Database. it's a no-cost feature vs being actually 'free'
If you're really worried - and there is no reason really - you could also use OpenJDK 11, but you wouldn't be supported by Oracle if you ran into any problems. I don't know of any issues with it, I just have to put that disclaimer out there.