The RedReader app has been given accessibility status by the graciousness of reddit and will not have to shut down. The dev is not particularly happy about how fellow devs were treated though and still plans on adding lemmy in future. Read the announcement here
My understanding is that one implication of the API cost is that it will impact the cost of running bots/automation of moderation tasks. If this is true, I don’t think it matters much that they are allowing some third party apps if all the subs get overwhelmed with spam and bots.