Apparently vesta (http://www.vestasys.org) can handle large binaries (it's from the EDA world, so this is plausible). It's open source, but the extent to which it's distributed is debatable - you need a server, but anyone can install a server and they form a distributed network like a dvcs.
Thanks, looks interesting, and it came from DEC via Compaq. It's billed as a Configuration Management System (i.e. managing builds). They do talk of managing tens of GB of derived data, which is also important.
The hardware part seems limited: "the Alpha group ... hardware description language files into Vesta's source code control", so not schematics or layout binaries as 'source'.
That site seems to be resting since 2006, but there is some activity at http://sourceforge.net/projects/vesta/ (releases in 2009, mailing lists with 2010 messages).
