The memory and CPU of DNS-323 cannot do a good job hosting SVN, just WebDAV access alone will kill the box. More importantly, not sure common folks even understand 'version control'.
If what you want is for the DNS-323 keeping old versions of your files, something like your recycle bin, you can actually get that with the samba in the box. What that does is that whenever you write over the existing file, the samba server will first rename the existing file (so, very little cpu resources consumed), then write the new content. This is the VFS feature since samba 3. DNS-323 has 3.0.24 (as of 1.08 firmware). One of my DNS-323 has this turned on, and it has been happy. However, the recycle bin is not accessible from your typical window via 'map drive', it will actually be a special folder that contain all old versions of your over-written files. You will need to set-up access security properly too.
However, to configure it, you will need to get into the box via telnet / ssh (dropbear), which requires you to install fun_plug. Once you are set-up for telnet/ssh, then getting something like recycle bin is adding a few lines of configurations in smb.conf. Try googling 'samba VFS recycle bin' to get some idea of what needs to be added. This is not for people who do not know system administration. Be warned that changing internal configuration file may lead to a dead DNS-323 if not done properly.