Backing up Neil:
At the moment, there are two ways fonts can be used in DPS 2015. 1) As part of an article. 2) As part of the app.
An article can either be exported from InDesign (pixel-perfect) or it can be HTML.
-- The InDesign article can use fonts that are licensed for use in a PDF or ePUB -- depending on the foundry's license. Specific faces in the Adobe Font Folio allow this usage. (Font Embedding Permissions | Adobe and specifically: Additional License Rights, font permission list | Adobe)
-- An HTML article might, someday, use something like a @font-face call in CSS, but this isn't supported yet -- but a call out to a web resource would be a problem for offline reading...
The second situation, a font built into the app, currently works for card design. But this isn't supported for use in an HTML article.
As Neil says, licensing fonts to be part of the app is a different use than as part of an article, so a foundry might require different licensing. The Font Folio resources above are for use in content, not in an app...
HTH -- Colin