Gisi, Mark:

All in all, from a compliance perspective - THERE IS NO BETTER PRACTICE THEN INCLUDING A CLEAR LICENSE NOTICE IN EVERY FILE.

Sure. However, in a world where a LARGE number of people intentionally include NO LICENSE and wrongly assert that "no license"=="I can do anything I want", I'm delighted to have *one* well-understood license with the software package. Github has since made major improvements, but this is still useful for context: http://www.infoworld.com/d/open-source-software/github-needs-take-open-source-seriously-208046. My "thanks" to the people at RIAA et al who have successfully convinced many in a generation that copyright is a no-longer-relevant or evil law and that "all the cool kids" ignore it :-(.

At this point I'm trying to get people to include a well-understood lawyer-and-OSI-approved OSS license SOMEWHERE in their project if they intend to release software as OSS. Getting license text into every file is lower in my priority list. It's hard to water the plants when the building is on fire.

But I agree that per-file is best. If you want a clear license notice in every file, it needs to be REALLY EASY to add. Adding a lot of text in a large number of files is less likely to happen.

--- David A. Wheeler