Can we use CCSV5 on TMS570 MDK?

The license window should give you the option to select the XDS100v2 license.  As long as you are using the XDS100v2 that is on the MDK then the license will work.  Once you use a different external emulator you would need to purchase a CCS license.  If you have already purchased a CCS license, I think you should be able to enter that license number into the license requirement window.   This is my understanding.   It you are still not able to make this work I suggest to post the question on the CCS forum.  http://e2e.ti.com/support/development_tools/code_composer_studio/default.aspx

Regards,

Roy