Yes, you should stay current. That doesn't necessarily mean GitHub, but you should at least have a pretty good idea of what GitHub is, what it does and how to use it.
Here's the thing. If you want to get a programming job today, chances are you'll need to pass through some kind of "white board" programming test. That is, a 1-3 hour session where the hiring manager and team will sit you down and ask you to come up with code and architecture to solve a real world problem. That means that you'll need to be able to think on your feet. It can be a terrifying, humbling experience if you are not prepared for it or even if you are. So, the best thing you can do is be prepared.
If you're selling yourself as a Java developer, you had damned well know Java inside out. Yeah, that means crack open a recent website and read up not just on all the fundamentals you've forgotten but also read up on some of the newer stuff that Java's added in the last few years. Walk through some sample interview questions on the web.
Secondly, work on your people skills. You'll have to be able to explain yourself clearly and concisely. You can be a brilliant technical person but if you cannot be understood, you won't get the job. During the white board session, people aren't looking for perfect syntax. What they are looking for is how you approach a problem, how you break it down, and how you communicate your path through the problem. Again, this all comes down to good communication skills as much as how well you sling code.
For the record: I'm a 53 year old programmer. I just "retired" from one company and landed in another with a 20% pay raise and better opportunities to move upwards. And yeah, I did have to pass a grueling 3 hour "white board" test. It can be done.