LaserMan will tell you that just 5 years you couldn't even remove the NTSC pulldown on a home computer. Yes there have been developments, but the software for branching is not in the public domain, heck even MGM doesn't have and can't produce high quality branched DVD's. what you have to understand here is you need more than just an encoder - you need a tool that actually exploits the DVD specification. That can write MPEG files that branch onto different ones. This isn't software that freeware developers are going to have an easy time writing.

Encoding DVD material is all very well and good until you have to encode a continuous stream that branches. It has to be able to remove a chunk AND have the MPEG stream follow seamlessly. Yes you might think "keyframe, doh" - but it's not that simple. As I've said, you can re-encode branched titles and painstakingly re-build the branching. That would be impossible if it was the stream itself that had to remain intact. Anyhow I'm way out of my league here, I'll let someone more qualified explain it if they choose to.