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If not, there's always the KVR classifieds.
I would recommend PMing one of the mods with this question, or perhaps flagging your post to bring it to the mods' attention.
I'm not a mod, but I would think it's allowed- I'm fairly certain I've seen software sold on this board before. I know for a fact someone recently had (or still has) a copy of TSE's X50v2 for sale. At least I've yet to see anything from the mod squad explicitly stating it can't be done.
Categorically I'd put it under Gear.