Click here for a long .mp3 audio recording of Oz Linden, Director of Open Development at Linden Lab (Scott Lawrence IRL) explaining the changes to the company's policies around third party viewers, which forbid a viewer which alters SL "in such a way that users on other Viewers don't experience the same virtual reality." The policy change has provoked a lot of controversy, in great part because its vague wording. In Oz's presentation, he tries to assure TPV developers that their contributions are valued and wanted, and that the policy change is meant to prevent abuses. At the same time, the developers he engages with seem resentful and distrustful, at least partly due to Linden Lab failings from years that were prior to Oz joining the company. But as it's a long talk, I've only heard snippets so far.
Give it a listen, and if you're a TPV developer or user, post in Comments the parts which give you most concern -- or the most reassurance. Be sure to include time codes!