regarding regular patches, I'm the only one with a write access to the official uBlas repository as I need to keep things coherent for official releases. Boost.uBLAS is used everywhere in the world and it's my responsibility to keep things clean as much as possible.
So the common and best practive is to post your patch on the mailing-list so that people can make their own branch and test it and comment on it. It's the common practice.
We're thinking about an open-ended git repository where authorized people could upload their patch too and the rest of us could download them through the normal git process. I'll keep you updated on that. Currently we have several git repositories on github, sourceforge and the Trac system at Boost. I'm merging everything. We also have a lot of places with documentations and FAQs and we will merge that into the main documentation as well.
I encourage any people interested in contributing to ublas to contact me either directly or on the ublas mailing-list. Well if you're reading this email, you've already subscribed to the mailing list.