>>"And technically different, then there seem to be some more or less
virtual solutions running on top of Android:
http://forum.xda-developers.com/showthread.php?t=1868377
http://linuxonandroid.org/complete-linux-installer-updated-to-v2-7/"

I have managed to run Ubuntu on my tablet on top of Android but the experience was really bad for me because the connection with Ubuntu is made through VNC makes it very unstable and sometimes unresponsive.  

>>"Let me clarify: I don't mean running gretl (with gtk) directly (and
locally) on the Android _platform_, but on the underlying hardware
device, after having installed Debian/Fedora on it.
(Installation of these Linux distros is likely not trivial, but that's
another topic.)"

I don't think that we will have a real dual-boot between Android and some Linux distro very soon, maybe Ubuntu Touch will be usable this year (but I don't know if Gretl runs on it due to it's different X server?)

Also I want to know if it's possible to set the size of the icons in the gretl toolbar because they are to small to use on a tablet.