The makers of the GMG .22, a fully automatic air gun, are considering open sourcing the design. Sales have not been good and they think there could be more money selling plans, kits and parts than fully assembled guns.
I think they should open source the design and release the plans and any CAD models under a Creative Commons license.
If they can create a community of builders and modders there could be a profitable business in selling parts, kits and upgrades.
This business model has worked well in the hobbyist electronics market where mini-industries develop around supplying parts and kits for open source hardware.
The company is running a poll on their website, asking if people would be willing to buy parts, rather than an entire gun.