You can use the following procedure to check-out the plug-in, feature and update-site projects from SVN. Then you can modify and build new versions.

First of all install Subversive in Eclipse
In Eclipse open SVN Repository Exploring perspective and add https://subversion.assembla.com/svn/saplink-for-abap-in-eclipse/ repository
Select the menu : “File -> New -> Other”
Select “SVN -> Project from SVN” in the Wizard
Choose the SAPLink Repository and click Next
On the Select Resource page click Browse and select the project that you want to checkout
Click Finish
On the Check Out As page select “Check out as a project with the name specified” and modify the project name if you want
Click Finish

Now, you can open the “Plugin Development” perspective and modify the project. When you finish your work, commit back your changes by right-clicking the project name and selecting the menu “Team -> Commit”.

(You can also select “Team -> Synchronize with Repository” to review the incoming and outgoing changes on the project and resolve the conflicts)