Are there plans to modify the current design to replace non-reproducible parts such as bolts with parts that can be manufactured on the machine itself, bringing the overall RepRap design closer to 100 per cent self-reproduction?
Yes - that is definitely one of the evolutionary paths to greater reproductive success. For the immediate future I will be concentrating on widening the list of materials that RepRap can build with (starting with electrical conductors). That widening will implicitly raise the proportion of parts that it can make for itself, of course.
What is the current limiting factor with regard to making the RepRap work faster?
House room. If you have a self-copying machine, and you copy it, your rate of working goes up: 2, 4, 8, 16, 32 times etc. In short, it can go as fast as you like as long as you have room for the machines.
You mention three areas key to reducing the cost of building a RepRap: the software used to send the 3D model files to the RepRap, the physical electronics for the RepRap, and the RepRap printer design. What are the major obstacles you have come up against in reducing costs in these areas?
To be honest, there haven't been any major obstacles. It has taken (and is taking) time, of course - there are only about 10 of us, and most of us have day jobs. But -- fingers crossed -- we haven't yet hit any insurmountable problems.
Can the RepRap recycle what it manufactures?
Yes, recycling has been built in from the start. Though I personally think that RepRap landfill is much more environmentally friendly; I'll get to that in a few sentences. The main plastic we are using is polylactic acid. Anyone can make this by fermenting starch, so if you have a few tens of square meters of land to grow a starch crop you not only have a self-reproducing machine, you have a self-reproducing source of feedstock independent of the petrochemical industry. And polylactic acid is completely biodegradable.
So if you make junk in your RepRap machine, or if something made in it breaks, you just throw it on your compost heap and six-months later it's ready to be dug back into your next starch crop. Thus we have a complete, carbon neutral (except for the power used by the RepRap machine -- about 40 watts; and you could easily run it off a photo-voltaic), local, recycling route involving no transport at all and no industrial production.
But I want to move to using a non-biodegradable resin. This too is sourced from biomass, but is stable in the ground. That means that the more reprapped goods that get made from it and thrown in landfill, the more carbon is taken out of the atmosphere and locked away for good. And, in 200 years when we have taken so much carbon out of the air to make stuff that anthropogenic global cooling is starting to be a problem, the landfill sites become our strip coal mines to save us.