Those looking actively for an alternative tablet that embodies the Open Source philosophy might consider the just-released Spark, which runs the Plasma Active UX, an open source platform based on Linux with KDE Plasma ecosystem.
According to Aaron J. Seigo, a self-proclaimed KDE hacker who presented the tablet, the Spark is aimed primarily at people who want a device which sports "an open Linux stack on an unlocked hardware and comes with an open content and service market".
At 200 Euros, it might be a hard sell though, even if it has a 1GHz Cortex-A9 based AM Logic system on chip (almost certainly the single core AML8726-M launched back in November 2010) which features an ARM Mali-400 GPU and - surprise, surprise - a proprietary HD video decoding engine.
Other features include 512MB RAM, 4GB internal storage with an SD card slot, Wi-Fi and a 7-inch 800x480 capacitive touchscreen display.
The case looks identical to the UPAD, otherwise known as the ZT280-C71. From the picture published by Seigo, one can see an HDMI port, two mini USB ports and an earphone hack.
Expect the tablet to come bundled with services like OwnCloud web hosting, Kolab, Kontact Touch as well as books from Project Gutenberg and *ahem* paid-for contents and apps.