Not knowing anything about it, is that true or is he just trying to hold us to ransom ?
The thing about currency is that it's both a unit of measurement and a state institution - not an asset in the strictest sense. Any gold reserves the UK has, for example, are assets, and are probably going to be split on a fair basis - or, at least, that's where the negotiations will start. But sterling isn't quite the same.
It's a unit of measurement in the sense that it's just something we base the price of things on. The UK only has limited control over its value anyway - the ultimate arbiter of the value of the pound is the open market. The UK can of course influence it by monetary (and to a limited extent, fiscal) policy. But in this sense, sharing the pound makes about as much sense as sharing the metre or kilogram. 8.3% of the metre wouldn't make sense.
More importantly, it's a state institution - which an independent Scotland will be leaving. It will have no right to its control - in the same way that they will have no representation in the UK parliament, or any sort of proportional control on the UN Security Council or NATO.
There is no existing currency union in the UK, either. The hint is in the name - union - multiple sides. There is no independent Scotland at the moment, so there is no currency union "asset" to be shared. A theoretical currency union will be a
new, bilateral
agreement - probably signed in advance of independence - between the two independent nations. Much like any sort of trade agreement, or immigration agreement that both sides might find mutually beneficial, for example.
It's pretty much scaremongering, really. Not taking the debt might not be seen as a default in the legal sense, but the very fact that Salmond is making this threat suggests that an independent Scotland has a moral - if perhaps not legal - obligation to take the debt - so the punishment (in the form of borrowing rates) will be reflected in a similar way. Not default rates - but bad rates nevertheless. In addition to that, the UK technically owns everything that Scotland owns at the moment, so if they want to play the "no assets, no debt" game, it could get very ugly - not only would an independent Scotland be debt-free, but
asset-free, too.
Although if that happened, I think the UK would just pull the plug on Scottish independence. Which could of course would be ugly, but from the UK's perspective, even a little foreign control over monetary policy is a
very big deal - bigger than pulling the plug on independence - and one that should have been blatantly obvious after seeing what has happened after nearly a decade of financial crises.