Solved it!
It turns out that the "served" directory was wrong. For example to read the repository
/opt/bitnami/frameworks/codeigniter
The svnserve command is:
sudo svnserve -d -r /opt/bitnami/frameworks
(-d tells svn should be running on background, -r tells the svn to use the following path)
And then the repository should be available at address:
svn://website.com/codeigniter
Don't know if changing the path is a good idea or not but it seems to do the job.