It is distributed under the terms of the GNU Lesser General Public License.
Read below for a small introduction or jump to :
mpathd

It dynamically update routing tables according to the state of the gateways and a set of rules set by the administrator.
The state of each connection is determined by sending through ICMP probes to one or more addresses.
Mpathd acts upon rules it reads from its configuration files and commands received through control connections.
mpath

Mpath can work either with command line arguments or in interactive mode.
mping

It is mostly compatible with the usual command line arguments and can be used in place of the system ping command for most operations.
Mping is a useful tool for diagnosing network issues in a multipath environement, and can also be used to compare packet loss, latency, jitter and overall routing efficiency between different providers.
mpwww

The round trip time, packet loss and optionally inbound and outbound traffic can be graphed for every gateway.
You may want to check out the live demo that is running on this server.