Who are Dreambox?
The Dreambox is a Linux-powered DVB satellite, terrestrial and cable digital television decoder (set-top box), produced by German multimedia vendor Dream Multimedia. It is very simlar to the DBox2 units. Its firmware is officially user-upgradable, since it is a Linux-based computer, as opposed to third-party "patching" of alternate receivers. All units support Dream's own DreamCrypt conditional access (CA) system, with software-emulated CA Modules (CAMs) available for many alternate CA systems. The built-in Ethernet interface allows networked computers to access the recordings on the internal hard disks on some Dreambox models. It also enables the receiver to store digital copies of DVB transport streams on networked filesystems or broadcast the streams as IPTV to VideoLAN clients. Unlike many PC based PVR systems that use free-to-air type of DVB receiver cards the built-in conditional access allows receiving and storing encrypted content.
The combination of third-party developers and network connectivity which facilitates card sharing, makes Dreambox use particularly common among enthusiasts and those who intend to obtain services without payment. Third-party software for this purpose is neither officially endorsed nor supported by Dream Multimedia and voids the official warranty; however, unofficial web sites support a large community of enthusiasts.
There have been a number of different models of Dreambox available. The numbers are suffixed with -S for Satellite, -T for Terrestrial and -C for Cable:
DM 7000 (discontinued)
The DM 7000 has 64 MB of RAM, 8MB of flash memory, a Common Interface slot, a dual smart card reader, a Compact Flash card reader, a USB 1.1 port, and an PATA (a.k.a. IDE) interface for attaching an internal 3.5" hard disk drive to convert the unit into a digital video recorder.
DM 56X0 (discontinued)
There was a 5600 and also a 5620 model. The only difference being that the 5620 included an ethernet port. Otherwise, the DM 56X0 models were a cut down version of the DM 7000 without an IDE interface. They did, however, include an RF modulator allowing them to be used with older TVs that lack a SCART connector.
The DM 7020 is essentially an updated DM 7000 with 96 MB of RAM, 32 MB of flash and an RF modulator. Changes were also made on the software side, utilising Open Embedded  for the base Linux operating system.
The DM 500 is the successor to the 5620 and is the smallest and cheapest Dreambox, with a 252 MHz PowerPC processor and Ethernet connectivity, as well as the standard features of a free-to-air (FTA) satellite receiver, including MPEG 1 & 2 hardware decoding, plus a single smart card reader.
The DM 7025 is essentially a DM 7020 with the ability to add a second "snap-in" tuner that makes it possible to watch one programme while recording another; it features a Xilleon 220 system-on-chip from ATi, integrating a 300 MHz MIPS CPU (instead of the traditional PowerPC), and 128 MB of RAM.
The Linux-based software used by Dreambox was originally developed for DBox2, by the Tuxbox project. The Dbox2 was a proprietary design distributed by Kirch Media for their pay TV services. The bankruptcy of Kirch Media flooded the market with unsold boxes available for Linux enthusiasts. The Dreambox shares the basic design of the DBox2, including the Ethernet port and the PowerPC processor.
The factory-installed distribution on the Dreambox is mostly available under the GNU General Public License (GPL) and uses standard Linux API's, including Linux DVB API and Linux Infrared Remote Control (LIRC). This configuration encourages enthusiasts to modify its functions, particularly in the form of so-called images such as SDT Da Vinci.
In addition, unofficial third-party conditional access software modules (CAMs or emulators) are widely circulated on the Internet that emulate the CA systems developed by VideoGuard, ****** Access, Conax, Nagravision, Viaccess and other proprietary vendors.