Here's a few IDE's for DarkBASIC not in any particular order (though I generally prefer DarkEdit)
DarkEdit
Waffle's
TDK's DarkIDE
Code Keeper
I would also recommend in preferred order though these are not designed explicitly for DarkBASIC:
Source Edit, Crimson Editor, and Smart Editor Professional. They are all free IDEs and you can edit the language files to highlight DarkBASIC keywords. They also allow macro implementation, customized tools and a host of other features. For large projects, I use Source Edit.
Enjoy your day.