They use the LGPL license. The idea is that you can make closed source programs that link to the Racket system as a library, but you must provide a version that is linkable to newer versions of Racket. But in Racket the macro expansions are a fundamental part so the more strict interpretation means almost that you must provide the original source code in plain text.
I don't know enough about licenses, perhaps this is only FUD. And my impression is that the intensions of the Racket creators is that closed source programs in Racket are allowed, but this looks like a gray area.
And the GPL license is more restrictive, but C/C++ has many less macros/templates than Racket.
(first mail) http://lists.racket-lang.org/users/archive/2012-April/051303...
(most relevant mail) http://lists.racket-lang.org/users/archive/2012-April/051319...
They use the LGPL license. The idea is that you can make closed source programs that link to the Racket system as a library, but you must provide a version that is linkable to newer versions of Racket. But in Racket the macro expansions are a fundamental part so the more strict interpretation means almost that you must provide the original source code in plain text.
I don't know enough about licenses, perhaps this is only FUD. And my impression is that the intensions of the Racket creators is that closed source programs in Racket are allowed, but this looks like a gray area.
And the GPL license is more restrictive, but C/C++ has many less macros/templates than Racket.