Hi,
Right now, Like you have mentioned the usb_cam has source code for wet build (catkin build). you just need to do the following to build it from source. (Note: I assume you are using ROS hydro or Indigo, It should work on groovy as well may be you can try it). But all that said, here you go:
$ mkdir -p ~/catkin-ws/src
$ cd ~/catkin-ws/src
$ git clone https://github.com/bosch-ros-pkg/usb_cam.git
$ cd ..
$ catkin_make
$ source ~/catkin-ws/devel/setup.bash
after the above you can verify using ..
$ roscd usb_cam
roscore on a new terminal
$ roscore
and then in the terminal where you $ source 'd your usb_cam code run:
$ rosrun usb_cam usb_cam_node
Make sure you have your camera connected, before running the above command!!! you view the captured image on rviz,
$ rosrun rviz rviz
hope this helps.
mk