Well, keep in mind that (for all practical purposes) you cannot make a programming language in dbpro, and you cannot compile an executable from a dbpro executable (without being adept at assembly and incredibly knowledgable about computers in general)
But (if you read the dbpro licence... which you should have when you pressed the big "i agree" button
) you get the licence to sell games made with dbpro when you bought the product, so no worries there. (other things like dark gdk you have to buy the licence seperately)
So it's really impossible to make a completely independent game development something or other using DBPro. However, there are alot of resources you can make (and sell) for use with dbpro.
There are tons of plugins for DBPro that were made independently by users of DBPro. Then, the game creators staff said "Hey, this is good," and they now sell it online.
but... as for the technicalities... im not really sure. You can look into formats for sound and object files, if you want to make a music or object editor.
I've seen a couple editors before that are used for setting up objects, that save a text file with the exact same name of the object, and in the .txt file, theres variables like position, rotation, and other things, so i guess i'd start out with making a text file, writing to it, and then reading from it.
make file "test.txt"
open to write 1,"test.txt"
randomize timer()
a=rnd(200)
b=rnd(200)
c=rnd(200)
d=rnd(200)
e=rnd(200)
write string 1, str$(a)+ str$(b)+ str$(c)+ str$(d)+ str$(e)
close file 1
this will write a string with 5 seperate random integers in one line. try pasting this code into dbpro and then reading what those numbers are.