SQL Server 2008 posibilities of having views from one database in another database?
Yes it possible, that's what three part naming is for.

Use the form: [DatabaseName].[DatabaseOwner].[TableName] when referencing your vendor tables.
ie:

CREATE View [ViewName]
AS
SELECT * FROM [VendorDB].[dbo].[TableName]


Regarding performance, there's no big performance impacts, if the table has appropriate index and statistics these will be used by your queries in your DB.

Note: If you specify an index hint in your query, these will be ignored unless you bypass the view and refer to the table directly.

Location of your DB
As Stan noted, the above assumes that the two databases are residing on the same SQL Server instance, if you want to have a view residing in a different SQL instance (and I do not recommend this), you can:


Setup a linked server to the Vendor
DB
Use four part naming in your view definition: [LinkedServerName].[DatabaseName].[DatabaseOwner].[TableName]  


ie:

CREATE View [ViewName]  
AS  
SELECT * FROM [VendorDBInstance].[VendorDB].[dbo].[TableName]