Read the official word from the makers of Masterplan.
The the folks behind Masterplan received a cease and desist email from a lawyer representing WotC, according to the Masterplan Blog
WotC’s objection, according to the blog post, is that Masterplan accesses data from the DnD Compendium.
Masterplan, in some ways, was delivering on the promises of DDI way back when 4E was rolled out.
Masterplan is in some ways what WotC’s Adventure Tools promised to be.