btcscript provides code and data structures to parse and execute bitcoin scripts. The scripting system bitcoin uses is a stack-based, FORTH-like language. It is not turing complete by design (as adding a full turing complete language opens up all sorts of potential complications and problems), but it still provides a fair amount of power.
As of late May 2013, there are over 238,000 blocks in the bitcoin blockchain and over 18 million transactions. This works out to be slightly under 11 GB of data when including transaction metadata. btcdb provides an efficient and relatively simple way to store and access this dataset from Go. Although it was built with btcd in mind, there are certainly other potential uses for it and we have designed the interface with that flexibility in mind. Unlike the other packages we have released, it is likely that there will be some minor interface changes as we continue to develop btcdb.