This is in the public domain, as is everything else in the universe.
File credits
Based on a technique featured in powerofthree's Simple Activate SKSE.
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Changelogs
Version 1.1
Fixed a crash related to doors that are only locked on one side. Previously, you would crash when you hover over the unlocked side.
Version 1.0
Initial Release
Which Key? NG
Have you ever been surprised when you activate a locked door, but instead of starting to pick the lock, you opened it with some key you don't even remember picking up? Do you miss Fallout 3 and New Vegas replacing the difficulty of the lock with the key that unlocks it? Here's a mod for you. Now when you look at a locked door or container while the key is in your inventory, the prompt will show the name of the key instead of the lock's difficulty.
I rewrote my original mod as an SKSE plugin, because while doing this in Papyrus is nice for compatibility, there's a noticeable delay between moving your crosshair over a locked door and the prompt updating to display the key's name. Now it's instantaneous.
Written against CommonLibSSE-NG, so one .dll supports all relevant versions of Skyrim SE. Currently does not support VR, because I don't have a copy of VR to reverse engineer and test with. It's probably not a fundamental incompatibility, it's just a matter of finding the right offset in the VR executable. PRs are welcome.