Update licensing explanation in README file

Related to issue #206

Author: boriel

README.md

@@ -9,14 +9,18 @@ ZX BASIC
 
 Copyleft (K) 2008, Jose Rodriguez-Rosa (a.k.a. Boriel) <http://www.boriel.com>
 
-All files within this project are covered under de LGPL3-like LICENSE
-(Read <http://www.gnu.org/licenses/lgpl.html>). 
-
-You can create closed-source (even commercial ones!) programs with this compiler
+All files in this project are covered under de GPLv3 LICENSE
+(Read <http://www.gnu.org/licenses/gpl.html>) except those placed in directories
+`library/` and `library-asm`. Those are licensed under MIT unless otherwise
+specified in the files themselves (i.e. a different license). Anyway, all of 
+the licenses for files under those directories allow binary closed-source
+(i.e. commercial) distribution of the files created with this compiler.
+
+You can create closed-source programs (even commercial ones) with this compiler
 (a mention to this tool will be welcome, though). But you are not allowed to 
-release the compiler itself as a closed Source program.
+release the compiler itself as a closed source program.
 
-If you modify *this* project (the compiler .py, .asm or whathever) files 
+If you modify *this* project (the compiler .py or anything licensed as GPLv3)
 in any way you MUST publish the changes you made and submit your contribution
 to the community under the same license.