NASA have their own implementation of the Bundling Protocol, called ION, which is also open source, but you have (or had) to jump through some hoops to get it. It use LTP as deep-space protocol transport, and is I believe 'kinda' interoperable with the DTN2 reference implementation. LTP is geared up for light-speed induced delays. DTN2 doesn't really offer much for deep-space work, but has support for some other interesting protocols, such as the Nack Oriented Reliable Multicast (NORM) protocol and I've been slowly knocking up support for the AX.25 protocol used by radio hams, and supported by the Linux kernel.