People are still selling fentanyl without a prescription. Is that legal?

Courts move slow, especially when the party being targeted has a lot of money. Them allowing Kalshi to operate isn't an endorsement, it just means they don't see what Kalshi is doing as a significant harm. The injunction to stop them from operating in Utah is still winding it's way through appeals.

Whether or not what they are doing is legal is not determined until they either settle, Utah drops the case, or the trail and appeals process determines that they are not guilty.