Even though there's a good bit of info out there about it, it's still a significant advantage for them. It could happen eventually, but I doubt it'll be any time soon.
I don't agree; as the article mentions, GFS is used for hundreds of different tasks within Google which encompass a massive range of use patterns. It's a general-purpose system, even if it didn't start as such.
It's no coincidence that the entire Google stack (GFS/MapReduce/Chubby/BigTable) has been replicated as open source: it's because it's a broadly useful set of tools for doing large-scale work with data. It would be useful for thousands of companies if it was open-sourced.
I'd wager that the reason Google isn't open-sourcing GFS is because it's a key part of the "secret sauce" which powers a lot of Google innovation: the sauce that allows a single engineer to slap together a massively scalable, useful application in his spare time. I think that separates Google from their competition more than any specific app does.
Thousands of companies might use if it was open-sourced, but I rather think many of the serious users are competing with Google, or could be competing in the future. It being part of the secret sauce is exactly why there's no percentage.
