I'm on what I assume is the latest beta t-engine4-windows-1.3.0b2 and I can equip most things anywhere...
Gloves as weapon for instance.
 
Shoes on head.
Pretty much anything goes afaik.
Drag an item from right side into slot.
Edit:
I had a mace and shield equipped and attempted dragging both a bow and a 2h in other slots, it wouldn't let me. "already has a similar item equipped in main hand"
Went and bought a ring to test equipping multiple same gears (two rings already) and dragged it to the (empty) arrow slot and the game basically froze but not "frozen" or "crashed", just toggling between a screenshot of 0.01s before I let go of the ring into the slot and completely black screen. 
Background town noises (birds in mageville) still playing periodically but otherwise can't interact with game. Ended in task manager.
Code: Select all
[LOG]	Bought:  #FFFFFF##UID:180641:0#steel ring#LAST# for 3.00 gold.
[MOUSE] pre starting drag'n'drop
[MOUSE] enabling drag from predrag
[MOUSE] ending drag'n'drop
fight: 	steel ring	arcing iron mace of massacre	::	nil	INVEN
fight: 	steel ring	steel shield	::	nil	INVEN
fight: 	steel ring	warrior's copper ring of lightning (#RESIST#)	::	nil	INVEN
fight: 	steel ring	Aleziladar the steel ring	::	nil	INVEN
fight: 	steel ring	Searpanic the copper amulet	::	nil	INVEN
fight: 	steel ring	brass lantern of clarity	::	nil	INVEN
fight: 	steel ring	impenetrable steel plate armour of implacability	::	nil	INVEN
fight: 	steel ring	Cloak of Deception	::	nil	INVEN
fight: 	steel ring	Steel Helm of Garkul	::	nil	INVEN
fight: 	steel ring	Girdle of the Calm Waters	::	nil	INVEN
fight: 	steel ring	iron gauntlets of the juggernaut	::	nil	INVEN
fight: 	steel ring	Noonshaper the pair of iron boots	::	nil	INVEN
fight: 	steel ring	sapper's iron pickaxe	::	nil	INVEN
fight: 	steel ring	arcing iron mace of massacre	::	nil	QUIVER
fight: 	steel ring	steel shield	::	nil	QUIVER
fight: 	steel ring	warrior's copper ring of lightning (#RESIST#)	::	nil	QUIVER
fight: 	steel ring	Aleziladar the steel ring	::	nil	QUIVER
fight: 	steel ring	Searpanic the copper amulet	::	nil	QUIVER
fight: 	steel ring	brass lantern of clarity	::	nil	QUIVER
fight: 	steel ring	impenetrable steel plate armour of implacability	::	nil	QUIVER
fight: 	steel ring	Cloak of Deception	::	nil	QUIVER
fight: 	steel ring	Steel Helm of Garkul	::	nil	QUIVER
fight: 	steel ring	Girdle of the Calm Waters	::	nil	QUIVER
fight: 	steel ring	iron gauntlets of the juggernaut	::	nil	QUIVER
fight: 	steel ring	Noonshaper the pair of iron boots	::	nil	QUIVER
fight: 	steel ring	sapper's iron pickaxe	::	nil	QUIVER
[LOG]	Bones wears: #FFFFFF##UID:180641:0#steel ring#LAST#.
Lua Error: /mod/class/uiset/Minimalist.lua:1137: attempt to index a nil value
	At [C]:-1 __index
	At /mod/class/uiset/Minimalist.lua:1137 displayResources
	At /mod/class/uiset/Minimalist.lua:2133 display
	At /mod/class/Game.lua:1562 
Lua Error: /mod/class/uiset/Minimalist.lua:1137: attempt to index a nil value
	At [C]:-1 __index
	At /mod/class/uiset/Minimalist.lua:1137 displayResources
	At /mod/class/uiset/Minimalist.lua:2133 display
	At /mod/class/Game.lua:1562 
(continues throwing this lua error until ended)
Note that it was still connected to chat and receiving messages/achievement notices internally, though again the renderer flipped out and was just toggling between black screen and same-screenshot [milliseconds before the mouse release] every 0.8s or so.
Loaded save reverted to entering magetown (for the first time) and vendors had different items.
Went to derth and bought a pickaxe and tried to equip two pickaxes, same blackscreen-screenshot toggling again.
Code: Select all
[LOG]	Bought:  #0080FF##UID:44967:0#iron pickaxe of delving (dig speed 37 turns)#LAST# for 58.20 gold.
[MOUSE] pre starting drag'n'drop
[MOUSE] enabling drag from predrag
[MOUSE] ending drag'n'drop
fight: 	iron pickaxe of delving	sapper's iron pickaxe	::	nil	INVEN
fight: 	iron pickaxe of delving	iron gauntlets of the juggernaut	::	nil	INVEN
fight: 	iron pickaxe of delving	Girdle of the Calm Waters	::	nil	INVEN
fight: 	iron pickaxe of delving	Steel Helm of Garkul	::	nil	INVEN
fight: 	iron pickaxe of delving	Cloak of Deception	::	nil	INVEN
fight: 	iron pickaxe of delving	impenetrable steel plate armour of implacability	::	nil	INVEN
fight: 	iron pickaxe of delving	brass lantern of clarity	::	nil	INVEN
fight: 	iron pickaxe of delving	Searpanic the copper amulet	::	nil	INVEN
fight: 	iron pickaxe of delving	warrior's copper ring of lightning (#RESIST#)	::	nil	INVEN
fight: 	iron pickaxe of delving	Aleziladar the steel ring	::	nil	INVEN
fight: 	iron pickaxe of delving	steel shield	::	nil	INVEN
fight: 	iron pickaxe of delving	Noonshaper the pair of iron boots	::	nil	INVEN
fight: 	iron pickaxe of delving	sapper's iron pickaxe	::	nil	QUIVER
fight: 	iron pickaxe of delving	iron gauntlets of the juggernaut	::	nil	QUIVER
fight: 	iron pickaxe of delving	Girdle of the Calm Waters	::	nil	QUIVER
fight: 	iron pickaxe of delving	Steel Helm of Garkul	::	nil	QUIVER
fight: 	iron pickaxe of delving	Cloak of Deception	::	nil	QUIVER
fight: 	iron pickaxe of delving	impenetrable steel plate armour of implacability	::	nil	QUIVER
fight: 	iron pickaxe of delving	brass lantern of clarity	::	nil	QUIVER
fight: 	iron pickaxe of delving	Searpanic the copper amulet	::	nil	QUIVER
fight: 	iron pickaxe of delving	warrior's copper ring of lightning (#RESIST#)	::	nil	QUIVER
fight: 	iron pickaxe of delving	Aleziladar the steel ring	::	nil	QUIVER
fight: 	iron pickaxe of delving	steel shield	::	nil	QUIVER
fight: 	iron pickaxe of delving	Noonshaper the pair of iron boots	::	nil	QUIVER
[LOG]	Bones wears: #0080FF##UID:44967:0#iron pickaxe of delving (dig speed 37 turns)#LAST#.
Lua Error: /mod/class/uiset/Minimalist.lua:1137: attempt to index a nil value
	At [C]:-1 __index
	At /mod/class/uiset/Minimalist.lua:1137 displayResources
	At /mod/class/uiset/Minimalist.lua:2133 display
	At /mod/class/Game.lua:1562 
To be clear I have zero addons installed besides item vault that's included in the download. I have stone warden disabled. All I did was extract 1.3b2 to a folder on my desktop and start playing skele bulwark.