I have been thinking on how to proceed with Plumhead, that is PHP on Parrot. The problem is that I have neither the ability nor the inclining to write a PHP grammar from scratch. So a template is needed. This brings up the question of licensing.
Johnlim's blog
PHP 5.2 is licensed under the PHP license, while parts are under the Zend license. Both licenses are BSD-like, which is quite acceptable to me.
So the plan of the day is to derive the Plumhead grammars from the PHP 5.2 grammar. I'm not sure whether that means that I need to put the whole of Plumhead under BSD license, or whether I can stick with Artistic+GPL.
Generally speaking, BSD-style licenses allow you to redistribute the original or your own derived works under any licensing of your choice. This would give you the right to relicense your derivative work as Artistic+GPL, which would probably be preferable for anything associated with Perl6/Parrot. You should check with the authors of the PHP license and see if they truly intend for this to be allowed. If they don't, though, they should be explicit about it in their license, and/or switch to a copyleft license such as the GPL.
The significant difference between the GPL license and the BSD-styles is the copyleft clause, which is actually implemented as a simple but significant restriction: works licensed under GPL (or another copyleft license) cannot be relicensed under another license, even when modified and redistributed. In other words, usually only the GPL license and a small handful of others intend for you to have license lock-in. The rest of them usually specifically wanted you to have the right to relicense your derivative works. (And in fact many people make a good living that way.)
