scponly is an alternative 'shell' (of sorts) for system administrators who would like to provide access to remote users to both read and write local files without providing any remote execution priviledges.
This has the very useful feature of being able to drop the user into a subdirectory on logging in, rather than leaving them in the chrooted root directory, which is locked down by its root ownership.
Neither cvs or released tar version compiles. Looks like this was reported in bug tracker 2yrs ago. In a modern sshd server you can set the shell to /usr/lib/openssh/sftp-server