I am certain that the bittorrent sync team have their own very well thought out reason for their licensing, whatever it may be. Yes, personally, I really cannot see the reason to not open source, especially if this product will be forever free, as in price, and since it's heavily involved with security (being a file sync-ing program), but who am I to judge their decision without knowing anything else about this project? I certainly am no legal expert either. But "Never say never, we still consider this option", is very good news, and pretty big as well. Since to change the licensing of a product will probably take a lot of thinking and what not (with their legal team etc). So just my two cents to try and nudge this decision. Quoting Emil Ivov "You cannot seriously talk about security in anything that is not open source, this is impossible." [source, 10:19 - 11:41 video on this page]. Yes I know this is fosdem, but the point stands. Now don't start debating 'security through obscurity', since that's irrelevant. What I mean is from an end user point of view. The only way end users (who care about this) can sleep tight at night is with the product being open source. Otherwise it simply isn't an option. This of course doesn't mean that they necessarily don't trust the company or dislike them or anything, just that it simply isn't possible to confirm what a company claims, which is a big deal when dealing with sensitive information. Now whether or not the btsync team will cater to these users and decide to open source is completely up to them of course. (And even if they do choose to do that, they have to choose what license and all, and that can be difficult as well.) But I have no doubt that due to the recent NSA PRISM leaks, there will be a large and growing proportion of users concerned about this. Now imitation is a form of flattery right? With the above, I still however have no doubt that btsync is a great product, there's simply nothing like this out there at the moment, call me much too enthusiastic, but I'd say this is quite revolutionary. I can pretty easily believe that btsync will become very popular regardless of the license (not that it isn't already), as in >= Dropbox popularity, since the main feature of dropbox is file sync (not cloud storage). (Especially with your upcoming mobile apps.) And that's also the same reason why I believe that, riding on the popularity of btsync, some sort of open source btsync will emerge. May not be as good as, or have all the features of this, but with such popularity, people will certainly at least try to come up with something. (Since btsync is at the least a very good 'proof-of-concept'.) And might I even dare to suggest that, if something does emerge (big if), it might become a threat to this. Since open source projects can grow quite easily, again popularity being the keyword, (now I'm starting to dream) but it may make say some sort of open protocol which may become standard or something etc. I know I'm just stirring stuff here, it may turn out that I'm horribly wrong, but I think some thought on btsync's direction here could go a long way. Collaborating with the rest of the world does in my humble opinion seem to be the best option here (from my viewpoint of course, I know nothing about what any real factors regarding licensing maybe, I can only postulate). Back to reality though, at the moment, in addition to FSF having this on their priority list (as binarybana pointed out), there also seems to be this (for what it's worth): https://groups.googl...ts/7WUj3nASuLo (which I'm in as well, I guess). I can though certainly understand, as this project still seems to be in early stages (somewhat, maybe not), that one reason for being closed source, is the maturity of the code. A company that plans on making a product open source may not feel that it's appropriate to release source code for something that's not ready yet or something. This happens all the time (the difference being that if they don't release the source code, they don't distribute binaries of the program either). So pretty sure btsync team already knew this but just in case. Anyhow, I'm taking this as great news, not taking anything for granted, but great news nonetheless. Now hopefully the time spent typing that was worth it. And thanks for reading this if you did. Peace.