mmmmmk here we go.
Wizards of the Coast, or Hasbro now, owns a lot of the words when referring to a TCG. "Tap" or "Tapping" and the "Tap Symbol" are all trademarked. Flying is not. Haste on the other hand...i'm pretty sure is trademarked.
Now i read "well its digital" and to be honest, that doesnt matter at all. If you dont know, Magic the Gathering has an online version as well. Its called Magic the Gathering Online. So they also should own digital trademarks as well.
My advice would be look into it and make sure, because WoTC doesnt play when it comes to Lawsuits, they will sue you over likeness rights in an "instant" (lol, see what i did there?). Thats why many, many, many CCG's died out, because WoTC basically owns everything. They were the first CCG to exist (if you didnt already know that) and they made it so that they will be the last ones standing.
Also remember, MTG has been around since 93. Almost 20 years now, and honestly, its all been done by them before. Coming into the world of TCG's is very tough in the fact that its hard to be 100% original because any hardcore MtG player can say "oh, thats this in MTG, they ripped that off". But the effort this game is putting out to be original is awesome. Thats why i'm about to donate 100 bucks to see this thing kick off.
Now with all that being said, i'd highly recommend the developers to really look into the wording and trademarks. It may sound stupid, but if you use one of them, it could cost you your business. Most people just arnt aware that they cant use words in a game, but its true, words as simple as "Spell", "Summoned" and "Tap" for example are very much trademarked.
Hope this helps!!