Thanks, Hotdoge3.
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I could not find a list explicitly stating the limitations of the free version. However, it appears that not all functions are limited: one should be able to extract SWF sub-sets from a complex Flash file, without problems.
Afterwards, using additional freeware, the SWF file segment can be converted to a still image.
For example, http://bytescout.com/ offers a freeware program called 'SWF To Image' which converts a SWF file to bitmap formats, like *.jpg or *.png.
'SWF To Image' can be downloaded from this page: http://bytescout.com/download/download_freeware.html
To serve as 'proof of concept', here is the process in action.
— Step 1. Download a free animation.
At random, I picked this freeware page for my source: http://screamdesign.daz3d.com/files/freebies/games/index.html
— Step 2. Load an animation into the decompiler and export to the SWF format.
Fig. 1.0
— Step 3. Load the exported SWF into the convertor and save it as a bitmap file.
Fig. 1.1
— Step 4. View the end result.
Fig. 1.2