L2 and L3 are essentially free for the purpose of making images and models for SE4 and SE5. You only have to register L2 or L3 if you want to make movies or if you're a nice guy and want to support Team DoGA.
It's true that L3's help files are in japanese, but if you spend a couple of days with L1 and L2 you can use L3 just fine.
I do have a translation of the L3 Parts Assembler help file on my DoGA fan page at
http://zircher.iwarp.com/doga.
In basic edit mode, L3 is just the same as L2 with a few more materials and shadow options. The power of L3 is that you can import your own textures, convert DXF files into parts, and change the texture projection settings on new or existing parts. This gives much more control. And, if you're a Metasequoia LE user, you can easily bring in new SUF (part) files via a menu.
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TAZ