I would rather say that Tizen seems to be quite alive under the Samsung umbrella & Maltemi is a big unknown at the moment.

UPDATE: I have a WebOS device (the HP Touchpad) an it is indeed quite a nice OS.

My biggest gripe ? The unavailability of a decent GUI toolkit for application development. You can either use the highlevel HTML/Javascript based Mojo or Enyo, but heaven forbid if you want to something more demanding than a form-filling app, work with files or do some more advanced graphics (I have heard about a developer who had to convert an image to list of 0 and 1 in JSON just to save it to disk). Oh and of course you application probably won't run anywhere else.

There is also SDL (it is mostly used by games), even with unofficial Python bindings. SDL is on the other hand rather rather low-level.

So what about Qt ? Actually, it is a part of WebOS 3 running on the Touchpad and a bunch of the UI is implemented in QML. But third party developers can't use it for their applications & it is not documented in any way !