> Is it related to libcoin? https://github.com/ceptacle/libcoin
Nope. libcoin is a fairly recent new project. libbitcoin is older.
> Does it (unlike Bitcoin) work on bigendian architectures?
Yes it works on big-endian architectures. Also Bitcoin is MIT licensed, whereas this is GPL.
> I can help you, but am already involved in way too many packages so
> would prefer that you (or others) stay in the loop and participate in
> the ongoing maintainance of the packaging.
I'd be willing to help engage and maintain the package, and work with the author of the package. I've got to make the software accessible to developers (as it is a library) so I'll do my best to help the Debian developers.
> Are you also considering packaging some of those projects that use this
Yes, eventually. I really like this project Electrum: http://ecdsa.org/electrum/ - I think it has massive potential in the future. Compared to other Bitcoin clients, there is no blockchain download and yet it remains secure. So it fixes the biggest usability problems existing currently with Bitcoin. However to get these projects working, the first step is to get their core dependencies out there. Electrum has mainstream appeal.
Another cool project using libbitcoin is subvertx which is a handy set of command line tools for working with Bitcoin. The ImageMagick of Bitcoin. Things like create private keys, download the blockchain into an SQL database, construct transactions and dump them offline to stdout, read from pipe and send raw transaction dump to network, examine private keys for addresses, check balances against the blockchain, ... .etc all these low level advanced commands. However it's not a priority since the usage is pretty niche, but I have a personal bias for anything command line :)
First step: libbitcoin.