Should not be an issue, the current XML API (v0.6) has been deployed back in 2009 and looks like it has been stable since then.

BTW, unless you are interested in writing an OpenStreetMap editor, you don't usually care about this API.

For writing OSM using navigation apps you usually use some of the third party APIs:

• POI search - like Nominatim
• routing - like OSRM
• parametric data search/dumping - like Overpass API

Please note all of these backends are open source sou you (or anybody else) can setup a new instance if the default one/ones go down for some reason.

This is quite an important difference to the Google provided APIs, that have no open backend and you are at mercy of them not breaking the API every week.

Also quite often you don't care that much about APIs and just use a dump of the OSM data (in the fast to process PBF format) and generate routing data or vector maps for your app from the dump. For example modRana does this for Monav ofline routing data.

Geofabrik provides nice and up-to-date data extracts for most countries. Alternatively you can also make your own extracts directly from the planet wide data dump - its actually quite easy.

So, please no ZOMG XML!!111 FUD...