TMO stands for Talk.Maemo.Org. It is a forum. It has a lot of people and a lot of posts. The software is hosted on repository.maemo.org and accessed through maemo.org/downloads/ and maemo.org/packages/. That has thousands of packages which encompasses the majority of third party software for Maemo.

There is also garage.maemo.org which provides developer support services (such as mailing lists and source code management).

So you are correct in saying that losing maemo.org would be a big deal. However:

• We are fairly confident we'd have some warning about a change in the funding status. Quim has recently said similar, but it won't hurt to ask for a reconfirmation.
• We are going to ask for a breakdown of costs so that if things do change, the community will know what sort of money is needed.
• There are a couple of mirrors of repository.maemo.org floating around. One was got up and running a couple of days ago: not much warning is needed.