The Subversion client can go through a proxy, if you configure it to do so.
First, edit your "servers" configuration file to indicate which proxy to use. The file's location depends on your operating system. On Linux or Unix, it is located in the directory ~/.subversion. On Windows, it is in %APPDATA%\Subversion. (Try "echo %APPDATA%", note this is a hidden directory.) There are comments in the file explaining what to do. If you don't have that file, get the latest Subversion client and run any command; this will cause the configuration directory and template files to be created.
Next, you need to make sure the proxy server itself supports all the HTTP methods Subversion uses. Some proxy servers do not support these methods by default: PROPFIND, REPORT, MERGE, MKACTIVITY, CHECKOUT. In general, solving this depends on the particular proxy software. For Squid, the config option is * # TAG: extension_methods # Squid only knows about standardized HTTP request methods. # You can add up to 20 additional "extension" methods here. # #Default: # none extension_methods REPORT MERGE MKACTIVITY CHECKOUT (Squid 2.4 and later already knows about PROPFIND.)
If it's difficult or impossible to get the proxy to allow Subversion traffic, but you want to check out the Subversion sources, you may be able to go around the proxy. Some proxies that filter port 80 nevertheless allow anything on port 81. For this reason, the svn.collab.net repository server listens on port 81 as well as on port 80. Try svn checkout http://svn.collab.net:81/repos/svn/trunk subversion and the proxy might let you through. Another strategy is to attempt the checkout over SSL, which many proxies allow: * svn checkout https://svn.collab.net/repos/svn/trunk subversion. Of course, your svn client will require ssl support; just pass --with-ssl to Subversion's./configure script to check. You can check to see whether the https scheme is supported by running svn --version.