Hi Wojtek,
Moving the server is also a hard decision for us to make, but taking lots of things into account finally we have to make this step forward.
We have been aware of the situation customer like you maybe in, we plan to move the customer projects to sourgeforge too, as stated in blackfin.uclinux.org:
Active proejcts on the old blackfin.uclinux.org server
If you have any active projects on the old blackfin.uclinux.org server and want to move to sourceforge.net, please send a email to ask for help.
Don't worry, we are not going to lose data.
Thank you for your interest and effort on Linux blackfin and we wish your effort could be continue on the sourceforge, this would make sense to others that used to and will benefit from your projects.