AstroVersion.The start page is where you add your repository URLs you want to view. It does not do check-ins and check-outs, but it provides all the view capabilities required to see a repos files, revisions and differences.
It is a Subversion repository online viewer written completely in Java with no pre-configuration needed.
Download the WAR, try it out ONLINE at http://astroVersion.webarts.bc.ca.
If you unpack the WAR, all the source files and ant build.xml are included to make any changes you want. (License: GPL)
You can even view AstroVersion source files online.
I use Jetty to run my webapps.