kdesvn/subversion is able to save passwords. Saving passwords is always a security risk, but may let a graphical frontend more usable.
Most secure way, but sometimes unhandy with GUIs like kdesvn. In particular the background processes of kdesvn would always ask for a password in case the repository has restricted access for reading operations like update and status. The same for “commit” and so on. So if you are not saving passwords you should disable Start check for updates when open a working copy and so on.
Secured password storage used by a lot of KDE programs like KMail and Konqueror. If you are saving passwords and mostly using kdesvn you should use this. Keep care that the encrypted storage isn't a high-secure storage. Details see KWallet documentation.
This is not recommended 'cause the passwords are stored as clear text! Not believing? Take a look into the files in
~/.subversion/auth/svn.simple. You should only use this if you are frequently using other clients than kdesvn like rapidsvn or esvn or the original svn command line client. If you're using the command line client mostly for checkouts or updates which do not require a password and kdesvn for commit/move/copy you should use KWallet instead.
You may activate an internal password cache which will hold passwords as long kdesvn is running in memory. So you must not enter a password twice even if you didn't save it in wallet.
When using subversion via svn+ssh password storage may done via ssh and ssh-agent. For this you must have ssh access to the remote machine and repository. When want to store something you should use the public key authentication of ssh, not the password authentication. (In fact ssh prefer the public key authentication). For this you must put your public ssh-key on the target, e.g., the repository system. SSH passwords will never be handled by subversion passwords storage or KWallet or internal password cache.
If you don't want asked for the password of your SSH key you can use the ssh-agent, with selecting the menu → you may store your SSH-key password for your current session so no further entering of your password is needed.