This one's going to be a bit of a different one this week since this character is probably known to you (Hell, the modern incarnation of them is getting a movie made about them), but you probably don't know that, due to how American Copyright law functioned between the 20s and 70s, this character is public domain. So, today let's talk about just how this happened.
[Disclaimer, I'm not a lawyer]
Now, most of you may be familiar with the current way things become public domain in America, mainly waiting a really long time for the property to enter it automatically. For The Great Gatsby, it took 96 years since publication for it to be free to use for anyone and everyone.
Most public domain superheroes became public domain in less time than that. In fact, they became public domain almost immediately because the relevant creators/companies did not file a copyright notice within 5 days of publication. This is the case of the Blue Beetle - specifically the original Dan Garret incarnation (it can also be spelt "Dan Garrett", but most people exploiting the public domain aspect of the character use the former spelling). The character was published and nobody filed that notice.
"But wait," I hear you cry, "didn't Charlton Comics get the rights to the character, and then DC got the rights from Charlton Comics?" - sort of. Again, the character is legally public domain, but they did purchase them anyway - more importantly, they also got the trademark for Blue Beetle, and that's an aspect you can't get around (also technically the Ted Kord incarnation of Blue Beetle is also public domain since their creators also didn't file a copyright notice, but do you really want to mess with that?).
Now, obviously their use by DC would be seen as a major risk for people wanting to utilise the character... but the reason I'm talking about this is that people have used the character anyway and have seemingly made it out unscathed. Project Superpowers (a modern reboot of a bunch of public domain superheroes) doesn't actually use him, but they were still bold enough to include him in a bios section in the back, under the name "Big Blue". Lucky Comics (a group that has also done licensed non-BBC Doctor Who Universe stuff, so they're pretty familiar with legal skullduggery) has a series called "Beetle Girl" about Dan Garret's granddaughter, Danni, who takes up her father's job as crimefighter. Most impressively, we also have a live-action movie called "Agent Beetle" about a modernised version of Dan Garret (but not so modern that they're the Jaime Reyes incarnation, which is undeniably copyrighted).
Basically, the Blue Beetle is a surprisingly safe pick... just be sure to call him something else (technically you don't need to call him something different within the comic/story - Beetle Girl uses "Blue Beetle" just fine within its pages, just not on the cover - you just can't use Blue Beetle in a way that infringes with DC's trademarks). Also make sure to not use anything added by a modern incarnation - Dan Garret was basically just a roided up cop in chainmail and didn't have any powers outside of that.