my opinion on secrecy of D license

[Charles D Hixson]

Yes, Python has a nice license.  So does Ruby.

D has the license that Walter has chosen.  He is the author, it is his
right.

Perhaps you should look at GDC?  It's thoroughly licensed under the GPL.
 It's not quite as far along a DMD, since for one thing the author has
less time to devote to it, and for another whenever DMD makes a change,
GDC has to play catch-up.  It's also not as easy to install.  (It
requires a recompilation of GCC.)  It used to be a part of the Gentoo
repository, but that seems to have disappeared (i.e., the last time I
had Gentoo installed I looked for it to install and couldn't find it).

My suspicion is that part of Walter's code is proprietary to someone
else, and that he licensed the right to use it while writing his C++
compiler...but not the right to reveal it.  He hasn't ever said so, however.

Still, if you want a GPL licensed compiler for D, GDC is what you're
looking for.  (If you want a MIT, BSD, or Artistic license, however,
there isn't one.  You'll need to write it yourself.)