More attribution, fix warnings and add screenshot image

LICENSE

@@ -20,3 +20,8 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+====== Textures
+- troll_eye.png and troll_shit.png come from the original troll mod and are assumed to be CC-0 (as per the ContentDB media license)
+- troll_smoke.png comes from MTG's tnt mod (tnt_smoke.png) and is licensed under CC-BY-SA
+- the emoji in the screenshot is the trolley emoji from Twemoji, licensed under CC-BY 4.0

README.md

@@ -2,3 +2,5 @@
 Troll your friends and foes nicely with this mod!
 
 All commands require the `troll` privilege to be used. See /help in-game for a list of available commands and usage.
+
+Based on the old [`troll`](https://github.com/Niwla23/troll) mod by Niwla23.

init.lua

@@ -21,7 +21,7 @@ end
 
 -- Check for troll commands that require things found in primarily MTG
 local function has_default()
-	return default ~= nil
+	return minetest.global_exists("default")
 end
 
 register_troll("t-ban", {