Just put these in a text file called mapper.txt and put that in the dosbox directory. make sure to make a backup of your old mapper.txt before overwriting it with this dvorak mapping.

hand_shutdown "key 290 mod1"
hand_capmouse "key 291 mod1"
hand_fullscr "key 13 mod2"
hand_pause "key 19"
hand_mapper "key 282 mod1"
hand_scrshot "key 286 mod1"
hand_decfskip "key 288 mod1"
hand_incfskip "key 289 mod1"
hand_cycledown "key 292 mod1"
hand_cycleup "key 293 mod1"
hand_recwave "key 287 mod1"
hand_caprawmidi "key 289 mod1 mod2"
hand_caprawopl "key 288 mod1 mod2"
hand_swapimg "key 285 mod1"
key_esc "key 27"
key_f1 "key 282"
key_f2 "key 283"
key_f3 "key 284"
key_f4 "key 285"
key_f5 "key 286"
key_f6 "key 287"
key_f7 "key 288"
key_f8 "key 289"
key_f9 "key 290"
key_f10 "key 291"
key_f11 "key 292"
key_f12 "key 293"
key_grave "key 96"
key_1 "key 49"
key_2 "key 50"
key_3 "key 51"
key_4 "key 52"
key_5 "key 53"
key_6 "key 54"
key_7 "key 55"
key_8 "key 56"
key_9 "key 57"
key_0 "key 48"
key_minus "key 39"
key_equals "key 93"
key_bspace "key 8"
key_tab "key 9"
key_q "key 120"
key_w "key 44"
key_e "key 100"
key_r "key 111"
key_t "key 107"
key_y "key 116"
key_u "key 102"
key_i "key 103"
key_o "key 115"
key_p "key 114"
key_lbracket "key 45"
key_rbracket "key 61"
key_enter "key 13"
key_capslock "key 301"
key_a "key 97"
key_s "key 59"
key_d "key 104"
key_f "key 121"
key_g "key 117"
key_h "key 106"
key_j "key 99"
key_k "key 118"
key_l "key 112"
key_semicolon "key 122"
key_quote "key 113"
key_backslash "key 92"
key_lshift "key 304"
key_z "key 47"
key_x "key 98"
key_c "key 105"
key_v "key 46"
key_b "key 110"
key_n "key 108" "key 108"
key_m "key 109"
key_comma "key 119"
key_period "key 101"
key_slash "key 91"
key_rshift "key 303"
key_lctrl "key 306"
key_lalt "key 308"
key_space "key 32"
key_ralt
key_rctrl "key 305"
key_printscreen "key 316"
key_scrolllock "key 302"
key_pause "key 19"
key_insert "key 277"
key_home "key 278"
key_pageup "key 280"
key_delete "key 127"
key_end "key 279"
key_pagedown "key 281"
key_up "key 273"
key_left "key 276"
key_down "key 274"
key_right "key 275"
key_numlock "key 300"
key_kp_divide "key 267"
key_kp_multiply "key 268"
key_kp_minus "key 269"
key_kp_7 "key 263"
key_kp_8 "key 264"
key_kp_9 "key 265"
key_kp_plus "key 270"
key_kp_4 "key 260"
key_kp_5 "key 261"
key_kp_6 "key 262"
key_kp_1 "key 257"
key_kp_2 "key 258"
key_kp_3 "key 259"
key_kp_enter "key 271"
key_kp_0 "key 256"
key_kp_period "key 266"
mod_1 "key 305" "key 306"
mod_2 "key 307" "key 308"
mod_3