A: MyUID is a universal login database. You can use it to allow users on your site to use their MyUID identity, rather than having them register a new one at each site they visit. It uses XML-RPC to communicate with clients, making it usable from almost any language with a properly written API.
A: The beta is out, check the download page.
A: Yes. However we have a strict policy as to what kind of advertising will be on MyUID. Things like popups which generally would annoy our users are prohibited.
A: No. MyUID is open as in, open access. The connectivity APIs are free and open source, but the base system is not. However, anyone will be able to connect their site to the MyUID database for free. Some services, such as transparent logins, might come at a price, but not ones vital to basic usage.