I want to keep Maemo 5 Fremantle as my operating system while changing the desktop environment.

Why?

I don't want to destroy everything by flashing another OS (flashing seems too radical for me),

and I don't like shiny interface of Hildon, along with transitions and blurs;
Hildon Application Manager is useless, I install almost everything from xterm;
File Manager is limited, so I currently use combination of Fennec for reading and xterm+vi for editing.

KDE and GNOME are too heavy; FVWM, LXDE, E17, Openbox or ICEWM could suit me. I don't know the differences amongst them; deep thanks for explanation.

I want the most light and configurable desktop environment, without losing functionality.
I prefer to have both real and virtual keyboard.
One desktop is enough, ten is too much.
Having two windows on one screen is a luxury; having only one window working at a time is a constraint (thus, multitasking is quite a necessity, though I could try to live without it).
Adobe Flash is not needed; Fennec is the best browser, in my humble opinion.

Having no shadows, no borders, no gradients in titlebars, statusbars, etc is fine.

Matchbox might be good; it's said to be minimal (very well!) window manager;

but currently Hildon has shiny, gradient buttons, backgrounds, transitions, sparks, blurs, etc, and I don't want them.

And I have no icons and no widgets on desktop.

Gestures support is also excessive. Tap, double tap and tap-hold are quite enough. Drag-and-drop seems to be unnecessary, too.



I have no memory card, just usual specifications of N900.

Why not go all out:

http://www.nongnu.org/ratpoison/

might look at something like this.

Nokia

Thanks for reply!

I downloaded 1.4.5 tar.gz, but how do I install it?

It's not a deb, I mean. Please, explain how to install tar.gz, or where to download deb for Maemo.

Uhhh...that was a joke...did you really check out the website? Look closer. Anyway, sorry if it went by you. It's not really installable on the N900.

Why not?

The tar.gz is source package, but it's structure isn't suitable for dpkg-buildpackage. So building ratpoison on maemo cannot be done by a newbie, but in principle, there should be a way to do it.
But I don't really need ratpoison; it would most likely have no touchscreen support, as it has no mouse support (source: Wikipedia).

So what about FVWM, LXDE, E17, Openbox, ICEWM, etc? What are the differences amongst them? What are working, light, fast, simple alternative desktop environments working on Maemo 5?

It's probably INSTALLABLE (if built for ARM), but it's not designed for N900. You wouldn't be able to access SMS, Phone, GPS, Camera... Anything useful.

Why not try install Android as a main OS and change the UI of android.

That's why I do not insist on ratpoison. I want something workable.

I want alternative desktop environment, not alternative OS.

Android would be difficult to install (like any alternative OS, if not more), slow to run (Java Virtual Machine), and it would be difficult to get apps for it (and to gain root).

It's a separate topic. I have already read enough about "Android isn't Linux", "Android is slow", "Android is nonstandard" to be glad that I have Maemo, not Android.




About changing user interface: I'm working on theme for Hildon which would expose Matchbox as it is, instead of using images here and there. But I would really prefer alternative desktop environment, which would have no fancy styling. Matchbox is good; GTK+ seems to be bad, at least theme-ing part.

Easy debian seems to be the ideal solution for you, it comes with LXDE and all the things you asked for. Have you tried it?

Wow! Man you're my exact opposite! Well if it is indeed yes! I suggest LXDE a total crap DU for me since it's way totally very simple and old school. Guess you would like it. Hehehe