This excerpt taken from the NDAQ 8-K filed Feb 20, 2008.
The DIFX transaction
In addition, as part of the Transactions, we, Borse Dubai and DIFX will enter into an agreement which provides that in exchange for $50.0 million in cash to DIFX and the entry into certain technology and trademark licensing agreements, we will acquire 33.3% of the equity of DIFX. We will also be responsible for 50% of any additional capital contribution calls made by DIFX, subject to a maximum aggregate additional commitment by us of up to $25.0 million. Closing of this transaction is conditioned upon the concurrent closing of the OMX acquisition. We have agreed to apply for a secondary listing on DIFX following the closing of the OMX acquisition.