Amanda, or the Advanced Maryland Automatic Network Disk Archiver is an open source computer archiving tool that is able to back up data residing on multiple computers on a network.
I am not a huge fan of having xinetd or perl on my system and this is reliant on both, however, there does not currently seem to be any reasonable open source alternatives that support managing a tape library.
My notes on setting this up were incomplete and woefully outdated so I removed them. I have included a couple of references to sources of specific information I either do or did find useful:
Cleaning a Tape Library
Any LTO cleaning tape may be used in any LTO drive