Licensing a file format (was Re: SVN Branch Description Format)

(CCing Semen Vadishev as I'd like to know if the SubGit project has any opinion about this)

If you haven't been following the thread - this is a discussion of a new format for describing SVN branching/merging/tagging behaviour. Among other things, this would let people plug different SVN exporters into different Git importers.

I'd like advice/opinions from the community about licensing the specification and reference implementation for this format, because it seems like establishing an open standard is a bit different to promoting open source. I've always thought of copyleft as the tool I use to promote sharing, but standards get more sharing by abandoning copyleft and relying on the network effect - forking a standard makes your product less valuable, unless you're not allowed to use the standard or you have so much market share you don't have to care about standards in the first place.

I'm planning to release the spec under a Creative Commons Attribution-NoDerivs license (i.e. commercial use allowed, changes have to go through me) and the reference implementation under an MIT license (i.e. blatant theft of the exact recommended behaviour is encouraged). This should minimise the barriers for people wanting to implement the format as specified, and maximise the barriers for people wanting to subvert the format. The downside is that it makes life difficult for everyone if I'm hit by a bus, and makes me less inclined to put some of the more complex algorithms into the non-copyleft reference implementation.

Just to be clear, the format is one of three parts involved in getting SVN branches/merges/tags into git. I plan to release an SVN exporter and git importer under the GPL, but expect to make a special case for the format.

So the big question - would you be more inclined to use/contribute to the SVN Branch Description Format if it had a different license?

	- Andrew