I guess you could download RC1-5 and upgrade between versions.
Another possible method is as follows...
- Download the RC5 and find the MySQL Server schema for that version
- Find the B5 schema
- Go to
http://www.syncsql.com/index.html and paste in the schemas to find any changed between versions and get the 'upgrade schema'.
- BACK UP YOUR EXISTING BOARD AND DATABASE
- Replace (source) files for the RC5 version
- Using phpMyAdmin or similar enter the 'upgrade schema' code.
...at this point you should have a working RC5 board, though you might also have a non-working board which is why one of the steps was to back up.