OpenLayers is a javascript library and does not require any installation.
Due to it's in-development nature, we do not keep a copy on the server.
Below is an example of the inclusion order for OpenLayers with geoExt functions.
If you are also using GeoEXT, you will need the extJS / Sencha libs as well. Please visit http://www.sencha.com/
<script type="text/javascript" src="extjs/adapter/ext/ext-base.js"></script>
<script type="text/javascript" src="extjs/ext-all.js"></script>
<script type="text/javascript" src="http://www.openlayers.org/api/OpenLayers.js"></script>
<script type="text/javascript" src="GeoExt/lib/GeoExt.js"></script>
For a simple OpenLayers page, you will only need line three of the above scripts.
