I dunno what this WiFi dude did…
I dunno what this WiFi dude did, but I’ve seen a ton of bars and restaurants demanding his freedom lately.
The humor in this joke lies in the fact that the jokester is intentionally misunderstanding the signs that bars and restaurants often have that say "free wifi". The real meaning of the signs is that they establishments are offering (to the consumers) free use of internet over wifi.
This joke is the jokester making fun of him or herself.