Darth... "professional" depends on your definition doesn't it?
if you look at it like this Lee is the one who really took the idea and made it something quite tangeable - he does have a professional background ... and not just within the games industry.
your title for the post and actual question are very different ... DarkBasic is not currently being professionally used as an alternative to C++ with DirectX direct, this isn't to say it'll never become a professional noticeable product though.
as for publisher support, you're not likely to grab the attention of any of the big time player companies without something that can actually compete with current titles...
but that said, publishers don't give a damn what something was programmed within - as long as its good enough to make money off of
Tsu'va Oni Ni Jyuuko Fiori Sei Tau!
One block follows the suit ... the whole suit of blocks is the path ... what have you found?