Just to signal a bug and it's workaround.
Mysql Ver 14.14 Distrib 5.6.23, for FreeBSD9.3 (amd64) using 5.2
Error: Field 'updated_by' doesn't have a default value
How to reproduce :
> Create a new project, and add one collaborator (me for instance) and save
> Edit the newly created project, add one or several more collaborators and save
> The error above show up
> Edit my.cnf mysql config file
> Remove "STRICT_TRANS_TABLES"