ioq3df is an engine for the Quake III Arena modification Defrag. It is a fork of ioquake3 to support Defrag specific features.

Auto download and auto load of single pk3 files for each map.
You can move all your map pk3 files from the Worldspawn Archive to the autoload/maps/ folder.
The auto download will download map dependency files to autoload/mapdeps/*.json and pk3 files to autoload/maps/*.pk3.
cl_mapAutoDownload [0/1]
cl_mapAutoDownload_source
fs_autoload [0/1]
New commands:
downloadMap
downloadPk3
downloadCheckMap Verify checksums for pak files.

Chat console:
To open the chat console use ctrl+tab or bind a key to one of the new commands:
togglechatconsole
chatclear
chatdump
+chat to use it like the scoreboard bind a key with \bind p +chat

r_defaultImage to replace the default (missing texture) images
i.e. \seta r_defaultImage "textures\liquids\bubbles.tga"

map_developer [0/1] cvar to show missing shaders, enabled by default

iodfe features by runaos:
snap hud:

iodfe_hud_snap_draw 1 - snapping hud, shows zones of possible acceleration (for 8 ms frametime)
iodfe_hud_snap_auto - auto-shifting angle of the hud for different strafe styles
iodfe_hud_snap_def - offset with no keys pressed or with scr_hud_snap_auto 0
iodfe_hud_snap_speed - calculate zones for the stated speed instead
iodfe_hud_snap_rgba1 - hud 1 color
iodfe_hud_snap_rgba2 - hud 2 color
iodfe_hud_snap_y - y position
iodfe_hud_snap_h - height

iodfe_hud_pitch - angle marks, setting it to "-15 70" for example will put two marks at -15 and 70 degrees of pitch
iodfe_hud_pitch_rgba - color
iodfe_hud_pitch_thickness
iodfe_hud_pitch_width
iodfe_hud_pitch_x - x position

con_timestamp [0/1] - adds a timestamp at each message in console
con_timedisplay [0-3] - displays time at input line (1), at right bottom console corner (2) or at both places (3)
con_drawversion [0/1] - toggles version at right bottom console corner

in_numpadbug [0/1] - fixes non-working numpad on Windows

r_xpos, r_ypos - game window position

Console shortcuts: Ctrl+Enter send chat message to team \team_say Ctrl+Shift+Enter send chat message to tracking player id \tell <df_mp_trackplayernum>

dfengine features:
con_useshader [0/1]
con_rgb
con_opacity [0.0-1.0]
con_height [0.0-1.0]

ioquake3 does use the folder %appdata%\Quake3 on windows to store config and such files.
If you want to use the original Quake install path add these start parameters:
+set fs_homepath "C:\pathTo\Quake III Arena"

You might have to reduce the cvar s_volume by 0.7 because of another sound backend.