It's not that it is "frowned upon" per se, just that all you are doing is taking one from the wild that won't be able to be returned once it's been in captivity for a while. And at the rate the cuban tree frog is taking over Florida, it's going to be a threatened species soon.
But here's the other issue. It's not a matter of buy stuff for it. When taking in a wild specimen, a fecal exam is an absolute must! So is swabbing for chytrid and mdb (?). So there's a few extra bucks. If any results come back positive, you have a vet visit in your future, along with meds.
Now, imagine you're sitting there saying bill's nuts, and you don't test them and unbeknownst to you, they DO have something and one day you handle them without gloves (because you ran our) and then put your hand in that pricey dart enclosure. A couple weeks later, your darts don't look good. Hmmmmm.......
I know that sounds exaggerated and melodramatic, but it is stuff that happens every day. Lija can tell you first hand what some bacteria can do to a household.
Honestly, buddy, hold him, have him say flies! take his pic and send him on his merry way
Education is the most powerful weapon we can use to change the world ~ Nelson Mandela