Your thoughts on JavaScript sourcemaps and picking a license for JavaScript

Regarding the use of FLOSS compatible JavaScript and their sources, what are your thoughts on the sourcemap technology? It is currently only supported in Chrome/Chromium (soon in Firefox), but it allows you to have easier access to the source code and debugging it in developer tools after the code has been minified in popular tools like Closure Compiler.

For example with jQuery, the minified version at http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js has the //@ sourceMappingURL=jquery.min.map line of code linking to the http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.map file in JSON format that the Chromium developer tools gain access to the jquery.js file with full debugging support.

Since this technology is new and many sites that run non-free JavaScript will probably not include sourcemaps, are you somewhat interested in its potential? Of course if the developer goes out of his or her way to offer source code in this method, it should be under a FLOSS license. More info at http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/

One more thing... when picking a FLOSS license for JavaScript, what do you think is the safest one to use? The BSD and MIT licenses are not copyleft, but then they don't force other code to be GPL if mixed with GPL code. How about MPL 2.0 which is a FSF approved file level copyleft license that is compatible with GPL 2, LGPL 2.1, and AGPL 3 and above?