Is this coffee maker safe to use?

Moka pots are traditionally rinsed (at most) but they're also traditionally used frequently. They develop a coating over time. If I'm putting mine away fro a long period I do clean it, after which it looks like yours, but mine is around 60 years old

If it was put away dry (not so much the top part as round the seals and up the pipe) and stored somewhere clean, I'd use it like that. If it might have got dusty, a rinse and wipe with a clean cloth might be in order. After prolonged storage you might even want to run it empty to rinse the pipe through and avoid stale coffee flavour. There's no need to use detergent unless you're resurrecting an old one or suspect it's been stored damp. Even then the inside of the pipe is the bit to worry about, and that's not easy to clean. A cloth wrapped round a chopstick is good for that, after removing the filter and seal (or you can buy culinary "test tube" brushes).

Just for fun, here's what mine looks like. It's normally used at least 3 times per week, and it's still wet from rinsing in the photo. I actually rinsed it a bit vigorously this time so loosened some bits of the layer of coffee that had built up