gPhoto is a free, redistributable set of digital camera software applications with support for nearly 400 cameras. It is available under the GNU General Public License. gPhoto runs on GNU/Linux, FreeBSD, NetBSD and other UNIX-like operating systems.
gPhoto has support for the Picture Transfer Protocol.
Many cameras are not supported by gPhoto, but have support for the USB storage protcol, which is well-supported under GNU/Linux.
gtkam is the official GUI client for gPhoto.
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