IMHO the FAQ page is somewhat misleading in that it minimizes the differences between the commercial and community editions
To the extent that this page is intended to help promote sales of the commercial edition, it seems to me that it hurts the effort by not mentioning ALL the differences and functions that are in the current commercial edition, but not in the community edition.
I know that based on the FAQ page, I just purchased the QCAD book by itself, since I didn't think that the drawing requirements that I have needed scripting or extensive poly-line support, which the FAQ mentions as the primary difference. (In retrospect I should have purchased the combo package of book plus commercial license, and I've just sent an e-mail to the "contact us" page asking if I can upgrade by paying the difference...)
In fact, I'm finding it a challenge to get through the exercises in the the book using the community edition as MANY of the features described are missing, or don't work as described...
Just getting to page 90 in the book, I've found the following significant differences:
(I'm using ver 184.108.40.206, Dec 12, 2008, compiled from Gentoo Linux sources)
1. Neutral Arrow - not there, but do get a left pointing arrow at the top of tools that will back you out with multiple clicks (p37)
2. Mouse cursor is NOT a yellow circle - instead you get a blue dashed cross-hair where the snap point is at, and a white cross for the mouse cursor. This can get confusing as the blue cross hairs can hide the blue "sample" line in some cases. (p39)
3. Window zoom - area to be zoomed is shown as a solid blue rectangle, not a dashed red one (p51)
4. Tool tip for extending
a line in edit mode says "TRIM
by amount" - not a big deal but confusing! (p64)
5. Autosnap function is missing in community edition - BIG annoyance! (p74, and lots of additional places!)
6. NO buttons to specify snap points by cartesian or polar coordinates (but this can be done on the command line) (p90)
7. Looking at the pictures, it appears the community edition also lacks the "snap to reference points" function.
(page references are to the QCAD book (english paper edition) where I found mention of the feature)
These differences are the ones that I found significant enough to make note of in the book, I'm sure there are probably others that I haven't gotten to yet. So far I've been able to work around the differences, but it has been a challenge in some cases to figure out how to do so.
My bottom line opinion is that the community edition is useable, but if the book accurately describes the functions missing from the community edition, but present in the commercial one, it would be worth the extra expense to get the commercial edition, especially if trying to learn QCAD by working through the book.
I am glad I purchased the book, so far it has been well written with good explanations and examples, and I'm finding it MUCH more useful as a learning tool than the reference manual.