Not really. .net apps have already been running on Mono, with varying success; there are also cross-platform apps built on .net - none of this should change sig

Not really. .net apps have already been running on Mono, with varying success; there are also cross-platform apps built on .net - none of this should change significantly. As for unmanaged apps - this changes nothing. Two things could happen: a) the open-sourced .net will allow for better implementations on other platforms, and/or b) MS will later step in as a patent troll and try to undermine Mono this way, SCO-style. While option B seems unlikely (the open-sourced code seems to be licensed quite freely), MS has played the Embrace-Extend-Exterminate card too many times for me to be entirely trustworthy.