It looks as though installing SQL Server 2012 Master Data Services alone on a web server that has no other SQL Server 2102 components doesn’t work out of the box. When you bring up the web page, you see an “Evaluation period has expired” page. Or at least I did, and so did at least one other person within the last week.
The workaround is to copy the file C:Program Files (x86)Microsoft SQL Server110Sharedsqlboot.dll to C:Program FilesMicrosoft SQL Server110Shared. In other words, replace the x64 version of sqlboot.dll with the x86 version (might want to save the old file just in case!).
More information can be found here.
Update (6/22/12): The problem returned after installing CU2. Same workaround.
Update (9/21/12): Ditto for CU3.
Update (10/18/12): Still happens with CU4, but the web.config permissions error problem (described elsewhere) was fixed.