diff --git a/COPYING.rtro b/COPYING.rtro
index 0697499..936358d 100644
--- a/COPYING.rtro
+++ b/COPYING.rtro
@@ -1,3 +1,77 @@
 Known derivative images:
-bear, polarbear: Reference photo by Amareta Kelly (https://www.flickr.com/photos/42409752@N07/6266114045/)
+bear, polarbear: Reference photo by Amareta Kelly (https://www.flickr.com/photos/42409752@N07/6266114045/), licensed CC-BY 2.0
 gloves_cloth: Reference SVG from Algot Runeman (runeman.org), via openclipart.org; distributed under CC-0.
+ape: Original is from RLtiles, a CC-0 collection of pixel art. Modified here under CC-0.
+wolf, dwolf: Derived from base wolf & dwolf, which are derived from RLtiles, a CC-0 collection of pixel art. Modified here under CC-0.
+bone_drake: Original is from RLtiles, a CC-0 collection of pixel art. Modified here under CC-0.
+elf_lass: Derived from clsc elf_lass, which is in turn derived from RLtiles, a CC-0 collection of pixel art. Modified here under CC-0.
+messageboard, messageboard_red: Referenced base image messageboard/messageboard_red, licensed under CC-0.
+dragonclaw_dagger: Derived from base image dragonclaw_dagger, licensed under CC-0.
+file: Derived from base image file, licensed under CC-0.
+
+Derivatives of unknown licensing:
+capitalhold_west: Referenced from base image capitalhold_west, of unknown licensing.
+out_tower: Referenced from base image out_tower, of unknown licensing.
+pagoda_tower_east: Referenced from base image pagoda_tower_east, of unknown licensing.
+hovels: Referenced from base image hovels, of unknown licensing.
+l_shop1: Referenced from base image l_shop1, of unknown licensing.
+rl_house3, rl_house_west: Referenced from base image rl_house3, of unknown licensing.
+university: Referenced from base image university, of unknown licensing.
+treefort, treefort2, treefort3, treehouse: Referenced respective base set images, and derived from retro tree_3, all of unknown licensing.
+archblack, archgold, archgreen, archtree, archwood: Referenced respective base set images, all of unknown licensing.
+brazier, unlit_brazier, firepot: Referenced base image brazier, of unknown licensing.
+lampost: Referenced base image lampost, of unknown licensing.
+broken_bird_gen: Derived from retro bird_gen, of unknown licensing.
+broken_scorpi_gen: Derived from scorpi_gen, of unknown licensing.
+horse: Derived from base image horse, of unknown licensing.
+broken_behold_gen: Derived from retro behold_gen, of unknown licensing.
+broken_devil_gen: Derived from retro devil_gen, of unknown licensing.
+broken_dragoncave, broken_dragoncave_blue, broken_dragoncave_green: Derived from retro dragoncave, of unknown licensing.
+ice_warrior: Derived from retro angel_knight, of unknown licensing.
+broken_giant_gen: Derived from retro giant_gen, of unknown licensing.
+broken_gnoll_gen: Derived from retro gnoll_gen, of unknown licensing.
+clown: Referenced from base clown, of unknown licensing.
+evilclown: Referenced from base evilclown, of unknown licensing.
+nun: Referenced from base nun, of unknown licensing.
+broken_bee_gen: Derived from retro bee_gen, of unknown licensing.
+chest_1_mimic: Derived from retro chest_1, of unknown licensing.
+broken_pixie_gen: Derived from retro pixie_gen, of unknown licensing.
+fire_troll: Derived from retro troll, of unknown licensing.
+broken_sarcophagus: Derived from retro vampiregen, of unknown licensing.
+broken_skull: Derived from skull_gen, of unknown licensing.
+bag_empty: Derived from retro bag_popcorn, of unknown licensing.
+vial_empty: Derived from retro vial_yellow (or any other), of unknown licensing.
+wbottle_empty: Derived from retro water, of unknown licensing.
+potion_empty: Derived from the retro potion styling, all of unknown licensing.
+crossroad: Derived from base crossroad, of unknown licensing.
+monument: Derived from base monument, of unknown licensing.
+store_food, store_food_barn: Derived from *really* old monochrome food shop image, of unknown licensing.
+woodwindow_0, woodwindow_1: Derived from retro woodwall and the style of retro wwindow, both of unknown licensing.
+awindow_0, awindow_1: Derived from retro woodwall and the style of retro wwindow, both of unknown licensing.
+redcwindow_0, redcwindow_1, westcwindow_0, westcwindow_1, dwindow_0, dwindow_1, dwindow_2, dwindow_3: Derived from retro cwall and the style of retro wwindow, both of unknown licensing.
+flagstone_win1: Derived from retro flagstone and the style of retro wwindow, both of unknown licensing.
+stwindow_0, stwindow_1, stwindowblue_0, stwindowblue_1, stwindowmossy_0, stwindowmossy_1, stwindowred_0, stwindowred_1: Derived from retro stwall and the style of retro wwindow, both of unknown licensing.
+window_0, window_1: Derived from retro wall and the style of retro wwindow, both of unknown licensing.
+b_axe1: Derived from base image b_axe1, of unknown licensing.
+dhaxe_1: Derived from base image dhaxe_1, of unknown licensing.
+dhaxe_2: Derived from base image dhaxe_2, of unknown licensing.
+shaxe_1: Derived from base image shaxe_1, of unknown licensing.
+handcrossbow, handcrossbow_bone: Derived from base image handcrossbow, of unknown licensing.
+reflexbow, reflexbow_bone: Derived from base set reflexbow/reflexbow_bone, both of unknown licensing.
+sflail_1: Derived from base image sflail_1, of unknown licensing.
+kama_1, kama_2, scythe_1, t_star1, twinblade_spear: Derived from respective base images, all of unknown licensing.
+giants_knife, hooksword, rapier, butterflysword_1, butterflysword_2, vlongsword, sicklesword: Derived from respective base images, all of unknown licensing.
+altarixalovh, altarsori, altarvalk, mbaltar_none: Derived from David Sundqvist's altar graphics, of unknown licensing.
+
+Original images with known licenses:
+jade_coin: Created by SilverNexus. Licensed as CC-0.
+amber_coin: Created by SilverNexus. Licensed as CC-0.
+dresser, dresser2, dresser2_cw, dresser_cw, close_dresser, close_dresser2, close_dresser2_cw, close_dresser_cw: Created by SilverNexus. Licensed as CC-0.
+punch_dagger: Created by SilverNexus. Licensed as CC-0.
+
+Images with attribution of author, but no known license:
+altardevo, altargaea, altargnarg, altarvalr, altargoro, altarlyth, altarmostr, altarnone, altarrugg: David Sundqvist (added 0.93.3)
+
+Known problem images:
+g_worm, purple_worm: These are ripoffs of Final Fantasy worms, and should be replaced.
+GreatDemon, medium_demon, fiend: These are ripoffs of the demon designs from 1994 DOS game Dark Legions. GreatDemon is basically a Dark Legions demon posterized to 3 colors, and medium_demon and fiend were derived from GreatDemon.