There’s a new (May 2014) BizTalk Server 2013 R2 Licensing Datasheet and FAQ. There are no changes to the licensing, but the updated datasheet adds in the Developer edition, has a (quite useful) table to compare editions, and includes a new FAQ right at the end which details the licensing limitations of BizTalk Branch edition.
Get it here: http://bit.ly/UR1LBt.
BizTalk Server 2013 Licensing Datasheet and FAQs from Microsoft. Useful sections include an overview of Core licensing for BizTalk, licensing BizTalk in virtualised environments, and how customers should move from Processor licences to Core licences. If you know your SQL Server 2012 licensing, then this is almost identical: http://bit.ly/1bLT7sr
BizTalk Server 2013 is licensed with the Per Core model and thus the Core Factor table has been updated to include it. Get the BizTalk and SQL Core Factor table here: http://bit.ly/1cgrHc3