I agree with @Allen15 assessment.  One fairly good use for a chain saw mill is squaring up posts from round logs.  Since the finish usually doesn't matter on a post (say, for a pole barn) and the wood lost is in slabs anyways, it makes more sense than in producing dimensional lumber.

Much of the design work in any saw mill is in the log handling.  Either the log is fixed and the saw moves down it or the mill is fixed and the log moves through it.  You either need a gantry of some kind (like the one Marcin had built for OSE recently), or some kind of carriage to carry the log as it moves into the saw mill.  In either case, you need some way to move logs.  Any log worth milling (say one foot in diameter or larger) is going to be larger than two men can lift.  Saw mills typically have a small crane or a grabber on a payloader to move logs around.

- mark

@Metz - The torchtable is an old can-or-worms issue that IMO, Marcin didn't like the advice he was getting about changing the design to something more suitable, & went to prototype with what they'd chosen instead - which didn't turn out to work quite as well as they'd hoped it would.
There are several other issues too, but that's my take, since I was the one giving the advice about changing, & I explained why to Marcin, & was then promptly asked if I would be willing to do it, which at the time, I didn't have the time, but I told him why doing it that way was prone to failure, and lo and behold, it never launched...
Now, it sits in the shop & was being used to pile junk on when I was there last month.
I think the folks who were working on it (or Marcin, or both) were so caught up on staying true to the RepRap design because they didn't have enough knowledge in the area to strike out on their own, wanted to re-use as much of the design work already done on the RepRap, and didn't really understand my explanation of how to go a different way using a few other existing open source projects for the guts, plus I think they'd already spent their budget on trying to supersize the RepRap design.
To answer your question, though, I believe the flurry of effort being put into a sawmill was at least in part, Marcin seeing a lot of money being spent on lumber to expand, and looking for a way to reduce or eliminate that line-item on the budget.
It is perhaps just as well that didn't go very far (for now), because if they'd built it, and then discovered that they really don't have anywhere near enough trees on site at FeF of sufficient size to get decent lumber out of, Marcin would be twice as mad about buying lumber, which they'd be back to needing to do, but now without a wind break of (small) trees in the winter...  To make matters worse, the documentation for such a sawmill would probably not have been done well enough for it to be a benefit to anyone else outside of FeF, where it might have actually been useful ;)

LOL yea!

I got in trouble when I worked for KBR Halliburton doing that.  When I started it was a great place to work.  Most of the people there were subject matter experts in their field. They did the job, no muss no fuss and that was it.  Then they started hiring a lot of people and did not check resumes.  I had one foreman who the fuel department whose prior job experience was caring for mentally retard children for the state social services.  Another guy totally lied on his application, I think he might have been a homeless bum before.  Then we had the former head of the USAF Fuel school and former head of fuel for the entire Iraq war hired as a foreman.  The other 2 yahoos told him he didn't know what he was talking about, and he quit in disgust. 

KBR the slogan was "Common sense is against company policy"

This is why I am choosing to work for myself, Well that and the coming new paradigm where if you are not a producer of real value you are gonna go hungry.

@spike - Most of the time you cut your slabs, then stack them all back up but rotated 90 degrees.  Now you cut 4 or 5 or 6 boards at once depending how big the log was.  Very fast.

Or, you take your slabs to a table saw with a feeder.  Bam....planks lay before you....:)

@Metz - Chainsaw mills are cheap, low production machines.  I own one in fact.  The "Alaskan Mill" type is simply a guide frame clamped to the chainsaw.  You clamp a straight board or rails to the top of the log, and then frame rides on that, keeping the chainsaw bar moving in a straight line at a fixed depth of cut.  After that you ride the first cut to make more cuts.  You can cut up a log where it falls, which reduces the weight you have to move out of the forest.  Drawbacks as mentioned above are kerf loss, the wide cutting teeth use up a lot of wood, and it's relatively slow.  For a one or two person operation that is going to be producing a house-worth of lumber, the appropriate device is a bandsaw mill, either one you make yourself, or hire.  I hired a guy with a Wood-Mizer brand trailer mounted sawmill, and the two of us were able to do around 1000 board ft a day from already gathered logs.  For non USA people, a board-foot is 12x12x1 inch (30x30x2.5 cm), it's the common measure of lumber volume.

The amount of wood you can cut per hour is mostly driven by the width of the blade and the horsepower of the engine driving the blade.  The difficulty of cutting wood only varies about a factor of two across all common species, so how much power you have is the main factor.  Note that once the wood is cut, you will need to dry it to a useful moisture content, and wood shrinks as it dries.  The slow and cheap method is air-drying.  Just stack the lumber with spacers so air can get around it, and have something on top to keep rain off, and something on the bottom to keep insects and moisture away.  Faster methods are solar greenhouses designed to capture as much heat as possible, and circulate the steamy air generated away from the wood, and full blown kilns, which are basically large ovens.  There is a huge amount of online literature on how to do all of this, and its not very hard on a technical level (I have done it, a lot), but it requires moving a lot of mass around if you are making a lot of finished lumber.

The *requirement* for lumber is fairly well defined.  It's about 6 board feet per square foot of floor space for conventional houses for framing, around 10 bf/sf if you count all wood uses, including furniture.  Other building types, like workshops or greenhouses have different amounts needed, but it's something you can look up in existing references.  Then the question becomes how many square feet of houses do you want to build, and how long to make them?  Is it just one for your own use, or 80 to house a village of 200 people?  From that you can size the machinery.  Same logic works for farm tractors.  If you are feeding 200 people, that converts to a certain amount of acreage, and then a certain amount of tractor engine power to do the job.  When feeding that many people, I would go for having 3 or 4 working tractors and 1 or 2 spares for reliability.  You really don't want your only tractor to break just before a critical time in the season.  So the general method is work backward from the needs you are trying to satisfy to the production output your equipment has to have, and then design for that.

Sharpening is a big pain with a chainsaw mill. Cutting a dozen softwood timbers is a good use for a chainsaw mill, but you can forget about using it with hardwood. A friend of a friend discovered that you have to do one resharpening per board when you are cutting red oak.