When the Dbpro upgrades were available they would periodically have a extras download starting with version 5.8, I believe. Here is the link to version 7.5 upgrade extras. The file name for DarkLights is LighMapper.dll.
http://files.thegamecreators.com/darkbasicprofessional/upgrade/dbpro_upgrade_7_5_extras.zip
Here is the keyword file I made for it.
LM Start==*no parameters*
LM Add Collision Object==Object Number
LM Build Collision Data==*no parameters*
LM Add Light Map Object==Object Number
LM Build Light Maps==Texture Size, Quality, Blur Radius
LM Set Blend Mode==Blend Mode
LM Add Point Light==PosX, PosY, PosZ, Radius, Red, Green, Blue
LM Add Directional Light==DirX, DirY, DirZ, Red, Green, Blue
LM Add Spot Light==PosX, PosY, PosZ, DirX, DirY, DirZ, Ang1, Ang2, Range, Red, Green, Blue
LM Clear Lights==*no parameters*
LM Clear Collision Objects==*no parameters*
LM Clear Light Map Objects==*no parameters*
LM Reset==*no parameters*
LM Set Ambient Light==Red, Green, Blue
LM Add Custom Point Light==PosX, PosY, PosZ, Radius, Zero Range, Attenuation, Red, Green, Blue
LM Build Light Maps Thread==Texture Size, Quality, Blur Radius
LM Get Percent==*no parameters*
LM Get Status==*no parameters*
LM Get Complete==*no parameters*
LM Add Light Map Object==Object Number, Base Stage
LM Add Transparent Collision Object==Object Number, Transparency Mode
LM Set Mode==Mode
LM Set Shadow Power==Power
LM Set Ambient Occlusion On==Num Of Rays, Ray Distance, Pattern
LM Set Ambient Occlusion Off==*no parameters*
LM Set Light Map Name==Filename
LM Add Light Map Object==Object Number, Base Stage, Dynamic Light Mode
LM Terminate Thread==*no parameters*
LM Add Shaded Light Map Object==Object Number, Light Map Stage
LM Boost Curved Surface Quality==Max Size, Multiple
LM Add Shaded Light Map Object==Object Number, Light Map Stage, Flat Shaded
LM Add Light Map Object==Object Number, Base Stage, Dynamic Light Mode, Flat Shaded
LM Build Light Maps Thread==Texture Size, Quality, Blur Radius, Num Threads
LM Build Light Maps==Texture Size, Quality, Blur Radius, Num Threads
LM Set Light Map Folder==Filename
LM Set Light Map File Format==Format index
Edit: The source code for DarkLights is available in the open source version on GitHub.
After a quick check of my archives, the extra downloads began with version 6.6.