Using Non-D&D 5e Modules in a D&D 5e Game

Can you add-on non-D&D 5e modules to one's D&D 5e game, e.g. the Pathfinder's War for the Crown Series to the Storm King's Thunder? Any issues converting material to the D&D 5e rule set?

You would have to do some work but nothing is stopping you from doing it. The work would mostly be the monster stats and other mechanical bits that would need to be reworked but the maps and fluff text would still be usable.

To clarify: each game (5e, pathfinder, etc) will use different attribute names - sometimes for the same monster stats (one game might use DEX, another might use Dexterity, etc).  The character sheet you are using will only display stats as defined on that sheet, so important say a Pathfinder module, you might miss a lot of of data. You can see most of the stats on the Attributes and Abilities tab, but they wont all hsow up there (any defined in repeating fields for instance, wont). So, if you plan to import a module for a different system, it's a good idea to ALSO create a campaign with the system it's built for, import the module into that, open it in a different browser, and then compare the stats in the two campaigns so you can see what data isn't visible.

And to add to the clarification GG made. Modules must be used as the basic foundation of the game aka the game must be created with a module. To move pieces of a module from one game you created to another you created, you will have to use the  Transmogrifier . This is a pro subscription feature. Addons are slightly different in their setup from Modules in the fact they can be added into into any current game. Just wanted it to be clear so there was no confusion in the various comments of importing 

Thanks, good to know. Basically it can be done using the merging process for modules and addons respectively. Thus the story, maps, and fluff are good to go, just have to watch out for any stats that may drop. Like the idea of creating a second game from the new module so the data can be compared in a second browser window.