But Oracle may suddenly change the licensing at some point in the future to something more onerous, so it would behoove you to consider not getting locked into MySQL now.
They can't change the license they already granted you. And moving now should not be any easier than moving in the event they do change the license in the future, with the added cost that moving may never become necessary. So, IMO, your comment on this issue is baseless fud. Developing a competing platform on tech you know to be patented is totally different than using validly licensed software.
If I'm running MySQL on some servers, and it works great, it's not going to suddenly explode, or stop working.