The ASF is made up of over 100 top level projects that cover a wide range of technologies. Chances are if you are looking for a rewarding experience in Open Source, you are going to find it here.
The Apache FtpServer is a 100% pure Java FTP server
The Apache FtpServer is a 100% pure Java FTP server. It's designed to be a complete and portable FTP server engine solution based on currently available open protocols. FtpServer can be run standalone as a Windows service or Unix/Linux daemon, or embedded into a Java application. We also provide support for integration within Spring applications and provide our releases as OSGi bundles.
OSGi framework implementation in C.
Celix is an implementation of the OSGi specification adapted to C. It will follow the API as close as possible, but since the OSGi specification is written primarily for Java, there will be differences (Java is OO, C is procedural). An important aspect of the implementation is interoperability between Java and C. This interoperability is achieved by porting and implementing the Remote Services specification in Celix.
VFS is a Virtual File System library.