I just wanted to mention that the U6 remake should generally be safe from legal action from EA, not because of any inherent "rightness" about what they've done, but because of the generally benevolent attitude EA has taken in the past concerning the core Ultima game remakes.
When I was on the Ultima Online team the U5: Lazarus mod for Dungeon Siege came out, and I actually chose a copy of Dungeon Siege II (if I remember correctly) for the weekly developer prize just so I could download the mod and play it. Our producer at the time was asked by the corporate legal department about it, and since it didn't harm UO, and possibly helped boost marketing recognition for Ultima in general, EA decided not to do anything as long as the remake didn't turn a profit.
In general, EA barely remembers the Ultima IP exists - except to co-opt it for brand recognition (such as the new web-game RTS). UO remains an excellent source of revenue for the company, but even with its millions and millions a year is considered extremely minor compared to the core franchises.
As long as the U6 remake team doesn't turn a profit from this, I couldn't imagine EA taking action, especially since the current UO team would still have a minor bit of input at Mythic. For the curious, no, server emulation for UO is not looked kindly upon by the legal department, yet no significant action was taken in all the years I worked there.
Meanwhile, for U6: I pray that the conversation system and scheduling systems have been converted. People remember Ultima 7 as the most "advanced NPC AI" yet U6 had almost all those features before they were perfected in U7, *and* the conversation system was a model for keyword/response recognition for any interactive games to follow. Ultima Online's own NPC speech system was based on U6's, boasting 13,000 unique lines of text before they were scrapped in 1999-2000 during a localization of the game where the translations were projected to cost something like $250k.
As with the Lazarus project, I just want to give my hearty thanks and appreciation to the team who created this. We dreamed of doing updated Ultima remakes at EA, but never gained any traction. Thank you for doing what we couldn't!